Side-by-side mattress testing · 144+ comparisons published
Updated September 2026
Category
Beautyrest Black L-Class
Plank Firm
Comfort
8.5/10
8/10
Support
9.6/10
9.5/10
Cooling
9/10
8.5/10
Edge Support
9.5/10
9/10
Motion Isolation
8.5/10
8.5/10
Durability
9.4/10
9.2/10
Value
8.4/10
8.8/10
Quick Specs Comparison
Spec
Beautyrest Black L-Class
Plank Firm
Price (Queen)
$2,799
$999
Type
Hybrid
All-Foam
Firmness
8/10
9/10
Height
13.75 inches
10 inches
Trial
100 nights
120 nights
Warranty
10 years
Lifetime (limited)
Shipping
Free white glove delivery
Free shipping
Key Advantages
Why Choose Beautyrest Black L-Class
- Firmest model — ideal for back/stomach sleepers
- Highest support rating in the lineup (9.6)
- Excellent for heavier sleepers (250+ lbs)
Why Choose Plank Firm
- Flippable — firm and extra-firm surfaces in one mattress
- Excellent for stomach sleepers
- Great spinal alignment
Lab Verdict
Cooling was a wash — both mattresses landed within half a degree of each other after 60 minutes of body heat. Motion isolation was roughly equivalent; either is safe for a partnered sleeper. Side sleepers will feel less shoulder pressure on the Beautyrest Black L-Class (peak 35 mmHg vs. 38 mmHg). Perimeter compression was nearly identical — neither bed is the obvious pick on edge support alone. Responsiveness was comparable; repositioning effort should feel similar on either.
| Metric | Beautyrest Black L-Class | Plank Firm | Edge |
|---|---|---|---|
| Cooling (60-min Δ°F) | 3.1°F | 3.5°F | Beautyrest Black L-Class |
| Motion isolation (g) | 0.13g | 0.13g | Tie |
| Edge sinkage | 1.8" | 2" | Beautyrest Black L-Class |
| Shoulder pressure (mmHg) | 35 mmHg | 38 mmHg | Beautyrest Black L-Class |
| Response time (s) | 0.5s | 0.5s | Tie |
| Off-gassing | 2 days | 2 days | Tie |
Median of 3 trials, 68°F climate-controlled lab. KW/BT / DH/NL · scoring vv2.1.