The larger step is much better, particularly if you're going to be doing any of her weight training workouts. She uses the step as a weight bench, laying down on it for chest and triceps work. The smaller step will not be as useful in that space (unless you're short enough). The larger, more expensive steps are also more sturdy in construction. I had bought a smaller step (from a different manufacturer) and ultimately ended up buying the larger step. The Reebok step is a little less expensive the The Step step and is adjustable to 6, 8 and 10 inches. It's also nice because the risers snap into the bottom, which makes for easier storage and transport.