I hate the elliptical trainer, but I love the arc trainer. I never even knew what the arc was until my trainer suggested it to me a year or two ago. Luckily my gym has about 10 arc trainers. The difference between the arc trainer and the elliptical trainer is that the arc footplates move in an arc path of motion and the elliptical moves in an elliptical pattern. I like how the arc feels better. Also, it’s supposed to be less stressful on your knees and body than the elliptical.