The NordicTrack T 6.5 Si delivers a 2.5 CHP motor (per Consumer Reports) and 12 mph top speed, outperforming the WalkingPad X21’s 1.0 CHP motor (per WalkingPad) and 3.7 mph limit. However, the X21’s fold‑up chassis (per CNET) and sub‑55 dB noise level make it far more suitable for tight apartments. For serious runners, the NordicTrack’s incline range and larger belt provide a clear advantage, w...