As a general rule of thumb: the more expensive a stair stepper, the better its quality. However, most high-end machines are quite large, making transportation and storage rather difficult. When working with limited space, consider compact or folding models.
The Stamina SpaceMate Folding Stepper (*Est. $130) may not be as sturdy and long-lasting as the StairMaster SC916 StairClimber (*Est. $4,300) nor as versatile and feature packed as the NordicTrack FreeStrider 35S (*Est. $1,000); however, it offers a sufficient home workout at a considerably lower price. Two hydraulic cylinders control the machine's resistance allowing for a smooth stepping motion. While the majority of users agree the SpaceMate offers enough resistance for a satisfying workout, a few feel unchallenged.
One of the pluses of the SpaceMate is that it folds to a manageable 38 inches long by 16 inches wide by 9 inches tall -- though possibly not compact enough to fit under some beds. Although its fully assembled size is also quite compact, measuring approximately 30 inches long by 16 inches wide, we did not find any user reviews noting stability issues.
The Sunny Health & Fitness Twist Stepper (*Est. $65) is even more compact without the need to fold, approximately 18 inches long by 16 inches wide by 8 inches tall. However, this piece of fitness equipment isn't a straightforward stair stepper. It comes with exercise bands and requires the user to twist. Similar to ice skating or roller blading, the exerciser's outside heel pushes down and outward in order to raise the inside foot, which pivots in the same rotation. Many users do not like the twisting motion, calling it awkward to perform. Like the SpaceMate, the Twist Stepper has a battery-operated display for time, distance, speed and an approximate calorie burn. However, the build quality of the SpaceMate far surpasses its cheaper counterpart, and owners do not feel they receive an adequate workout from the limited motion of the Twist Stepper.
For portability purposes the Twist Stepper might be the wiser choice. But, judging overall, the SpaceMate will give you much more satisfaction for not much more money, especially because it is reportedly more durable than the Twist Stepper, which is known to break in as little as two months.