The NordicTrack T 6.5 Si excels for dedicated running sessions with its 10 mph top speed and 10% incline per typical treadmill reviews, while the WalkingPad X21 targets desk-based walking at a maximum 3.75 mph with no incline. NordicTrack supports up to 300 lbs versus 220 lbs on the WalkingPad, but the latter's compact form wins for space-constrained offices. Choose based on primary use: full w...