Both a stair climber and stepmill allow you to mimic walking up steps, and both provide a vigorous cardiovascular workout while toning muscles in your legs and buttocks. Both machines can be difficult to use, so be prepared for a challenge. As similar as these machines are, some key differences exist. One is price: a stepmill, with its more intensive construction, is typically more expensive than a stair climber.
A stair climber consists of two pedals -- one for each foot -- that move independently of one another. Costlier versions have motors, while less-expensive climbers have air-pressure pistons. As you use the climber, one foot moves up while the other moves down. The stepmill works differently, providing a cascading staircase that you walk up just as you would the steps of a building. Stepmills always have motors, and are typically bulkier than stair climbers. While climbers allow you to set a resistance level, a stepmill allows you to select a speed, and your body weight provides the resistance.