Hi,
I have always used a 6" step with Cathe's videos. You're gonna work up a major sweat and get a great cardio workout regardless if you use a 6" or 8" step. A few weeks ago, Cathe herself even mentioned (in a post somewhere on this forum) that she had switched to a 6" step herself. I can't remember why she said that she switched. For myself, seems like I can give it my all as far as intensity with a 6" step, whereas with an 8" step, I spend too much time trying not to trip up and I end up with a less intense workout. I guess my point is, use what you're comfortable with. I find 8" very uncomfortable. Happy stepping!
Lisa