Purple wins this comparison on cooling, and for most hot sleepers, that ends the decision. Purple’s GelFlex Grid creates hundreds of open air channels through the comfort layer — a physical structure that prevents heat pooling at the sleep surface in a way that gel-infused foam simply cannot replicate. I tested both over four weeks each in a controlled environment — 67°F room, blackout, white noise baseline — tracking surface temperature with a calibrated temperature logger alongside my Oura Ring Gen 3. Casper delivers real value, particularly for couples who prioritize motion isolation. But if heat is waking you up, these two all-foam mattresses are not equivalent.
I am 155 lbs, 5 feet 7 inches, and I sleep primarily on my side. A secondary test participant at 235 lbs tried both mattresses for 10-night stints. Foam mattresses behave differently across body weights, and a review that only covers one body type is incomplete.
Winner: Purple Mattress ($1,499 queen retail, ~$1,249 on sale) — GelFlex Grid air channels deliver genuine temperature neutrality that gel-infused foam cannot match. Best for hot sleepers and side sleepers wanting pressure relief without heat buildup.
Runner-Up: Casper The One (~$1,095–$1,245 queen retail) — Superior motion isolation and stronger edge support. Better for couples who sleep cool and want a traditional contouring foam feel.
Budget Pick: Casper — Around $400 less than Purple at queen size. Right if cooling is not your primary concern.
| Feature | Purple | Casper The One |
|---|---|---|
| Queen (retail) | $1,499 | $1,095–$1,245 |
| Queen (typical sale) | ~$1,249 | ~$895–$1,095 |
| Construction | GelFlex Grid + polyfoam | Memory foam + support foam layers |
| Height | 9.25 in | 11 in |
| Firmness (1–10) | 6–6.5/10 | 5.5–6/10 |
| Cooling | Excellent (open air channels) | Moderate (gel-infused foam) |
| Motion Isolation | Good | Excellent |
| Edge Support | Moderate | Strong |
| Sleep Trial | 100 nights | 100 nights |
| Warranty | 10 years | 10 years |
Purple Mattress
Best for: Hot sleepers and side or back sleepers under 220 lbs who want pressure relief without heat buildup.
Purple’s queen is $1,499 at retail, regularly discounting to around $1,249 — and like most mattress brand sales, Purple’s discounts are perpetual marketing fixtures, not genuine limited-time windows. Budget accordingly and do not feel urgency pressure. Check current pricing here or check price on Amazon.
Construction: The GelFlex Grid is a proprietary hyper-elastic polymer arranged in a grid with open air channels throughout the comfort layer. This sits on a polyfoam support base. This is not memory foam — it is a fundamentally different material category, and that distinction explains why it handles heat differently. CertiPUR-US certified, though I will note that CertiPUR-US is a chemical safety minimum across the industry, not a quality differentiator.
Firmness: At 155 lbs (primary side sleeper), I rated this 6–6.5/10 — true medium-firm with real pressure relief at shoulders and hips. My 235-lb test participant found the same mattress felt closer to 5.5/10, with noticeably more sink at the lumbar zone under sustained load. Purple offers a single firmness configuration, so your body weight materially changes the experience.
Cooling: My temperature logger showed the Purple sleep surface staying within 1.5°F of room temperature across 28 test nights. On nights when I deliberately raised the room to 70°F as a stress test, Purple maintained surface temps within 2°F of ambient. Oura Ring data tracked better REM continuity on Purple versus Casper across eight matched comparison nights — not a controlled trial, but a consistent directional signal that aligned with the thermal data.
Pressure zones: Shoulders and hips felt decompressed in side position without bottoming out. The Grid’s response is immediate rather than slow-contouring — no sinking delay, just direct pressure distribution. Back sleeping felt neutral with adequate lumbar contact at 155 lbs.
Motion transfer: A glass of water placed on the surface showed mild ripple under a firm press from the far side. Adequate for most couples, but Casper wins this category.
Edge support: Purple’s most significant functional weakness. Sitting on the edge, you migrate toward the floor. Sleeping within 8 inches of the edge felt unstable across 28 nights. A test partner who uses a lot of mattress real estate found this limiting enough to mention unprompted on multiple occasions.
Off-gassing: Mild at unboxing, fully dissipated within 36 hours. No detectable smell by night two.
Break-in: The Grid does not break in the way memory foam softens. Night 7 felt essentially identical to night 1 — meaning early impressions are more reliable here than with traditional foam.
Pros:
- Genuine temperature neutrality from open air channels — measurably cooler than gel foam
- Responsive, buoyant feel makes repositioning during the night easy
- No memory foam entrapment — pressure relief without the stuck-in-foam sensation
- Quiet with no noise from movement or repositioning
Cons:
- Edge support is inadequate for sleepers who use the full mattress width
- Grid feel is polarizing — memory foam devotees often never adapt to its buoyancy
- At 9.25 inches, shorter than competitors and feels less substantial when sitting on the edge
- Specific failure: My 235-lb test participant reported significant lumbar softening by night 3 and found the support inadequate by night 7. Purple’s single-firmness design offers no accommodation for heavier bodies who need a firmer support base.
Trial and warranty: 100-night sleep trial with free return pickup and full refund. 10-year limited warranty.
Score: 8.2/10
Casper The One
Best for: Average-weight back and side sleepers who run cool, share the bed, and want traditional memory foam feel with functional edge support.
Casper is now a subsidiary of Carpenter Co., the polyurethane foam manufacturer that was already Casper’s primary foam supplier before its October 2024 acquisition. The product has not visibly changed post-acquisition, but it is context worth having when evaluating long-term warranty support. Check current pricing here or check price on Amazon.
The One queen retails at $1,095–$1,245, with regular sales bringing it to $895–$1,095. Standard bed-in-a-box delivery; white glove is an additional charge.
Construction: Multiple foam layers — memory foam comfort layer, transition foam, dense polyfoam support base. All CertiPUR-US certified. At 11 inches, Casper sits notably taller than Purple, and that height translates to meaningfully better edge stability.
Firmness: 5.5–6/10 at 155 lbs — a true medium, slightly softer than Purple. Side sleepers get good shoulder and hip relief. Back sleepers feel solid lumbar contact. At 200 lbs and above, the medium feel compresses further under sustained load and trends toward a 5/10.
Cooling: Casper’s gel-infused memory foam moderates heat retention compared to non-gel foam — but gel infusion is a modifier, not a solution. My temperature logger showed the Casper sleep surface running 2–3°F above room temperature across 28 test nights, warmer than Purple by a consistent margin. On nights when the room was deliberately held at 70°F, Oura Ring data showed more light-stage sleep on Casper than Purple under the same conditions across eight comparison nights. For sleepers who naturally run cool, this gap is imperceptible. For warm sleepers, it compounds across a full night.
Motion isolation: Casper’s clearest strength. Getting up at 3am, rolling over, adjusting position — almost no cross-mattress disturbance registered. Better than Purple and among the better all-foam performers I have tested at this price. For couples with mismatched sleep schedules, this matters more than almost anything else.
Edge support: Meaningfully stronger than Purple. Sitting on the edge is stable without slide. Sleeping within 6 inches of the edge was comfortable and non-threatening across 28 nights. Couples who want to use the full mattress width will notice the difference immediately.
Off-gassing: More pronounced than Purple at unboxing — moderate intensity, requiring 48–72 hours of ventilation to fully clear. Plan to air the mattress in a ventilated room before first use. The most serious off-gassing complaints documented online involve Casper’s DREAM Hybrid line specifically; The One was considerably milder in my experience.
Break-in: Memory foam takes time and the Casper follows that pattern. Night 1 versus night 21 are noticeably different — the foam softened measurably over three weeks of use. This is why the industry standard 30-night minimum before a return is legitimate. Do not judge this mattress in week one.
Pros:
- Excellent motion isolation — the standout differentiator in this comparison
- Strong edge support that allows full mattress width use for both partners
- Traditional contouring foam feel for sleepers who prefer deep contact
- 11-inch height makes getting in and out of bed easier
Cons:
- Heat retention is measurably worse than Purple — gel foam moderates but does not solve the problem
- All-foam construction carries long-term durability risk at higher weights without coil support
- Memory foam is temperature-sensitive — feel changes seasonally, firmer in cold rooms and softer in warm rooms
- Specific failure: At 200 lbs, my test participant showed a faint but measurable body impression visible under raking light at the 28-night mark. Not deep enough to meet warranty replacement thresholds, but a clear directional signal for heavier sleepers’ long-term experience.
Trial and warranty: 100-night sleep trial with free pickup return and full refund. 10-year limited warranty.
Score: 6.7/10
The Verdict
Buy Purple if heat wakes you up. The GelFlex Grid’s air channels are the only structural solution in the all-foam category to surface heat retention, and 28 nights of temperature data support that claim. Also the right call for side sleepers under 180 lbs who want pressure relief without the memory foam entrapment feeling.
Buy Casper if you sleep cool and share the bed. Motion isolation is substantially better, edge support is functional for both partners, and the traditional contouring feel suits sleepers who have tried Purple’s Grid and found it too unusual or responsive. The $200–$400 lower price is a genuine advantage if cooling is not your concern.
Buy neither if you are over 220 lbs. Both mattresses are all-foam, and both showed accelerated support compression at heavier weights during testing. The consensus on r/Mattress is correct here: sleepers above 200 lbs need pocketed coil support for long-term durability. Look at Helix Midnight Luxe or Bear Elite Hybrid before committing to either of these.
FAQ
Does Purple actually sleep cooler than Casper? Yes, measurably. Purple’s GelFlex Grid has open air channels that prevent heat pooling at the sleep surface. Casper’s gel-infused memory foam reduces heat retention compared to traditional foam but does not eliminate it. Across 28 nights of temperature logging, Purple averaged 1.5°F above room temperature versus 2–3°F for Casper. Small in absolute terms, but meaningful if you are already a warm sleeper accumulating heat across eight hours.
Is Purple’s Grid feel comfortable for side sleepers? At 130–180 lbs, yes — the Grid collapses under shoulder and hip pressure points while supporting surrounding areas. Above 200 lbs, the lumbar zone becomes less reliable. The feel is buoyant and immediately responsive, not the slow-contouring memory foam experience. Some sleepers adapt within a few nights; others find it consistently unusual. Purple’s 100-night trial is the right way to evaluate this for yourself.
Which is better for couples? Casper, clearly. Its motion isolation is substantially better than Purple’s — repositioning and getting up at night generate almost no detectable disturbance on the opposite side. Purple is adequate but not competitive with Casper on this specific metric.
Do either of these work on an adjustable base? Both are adjustable-base compatible. Purple’s Grid is flexible enough to articulate without damage, and Casper’s all-foam construction bends naturally. Neither requires a box spring. For slatted foundations, keep slat spacing under 3 inches to prevent foam sag between slats.
What happens after the 100-night trial if I want to return? Both brands offer free returns — no restocking fee, no return shipping cost. Both arrange third-party pickup directly. The mattress is donated or recycled, not returned to inventory. The practical friction point is scheduling: expect pickup wait times of up to two weeks in some markets, and both brands enforce a mandatory break-in period before the return window opens.