Wantfit,
Kathy S. Pilates are more of a basic in nature, there are some harder moves. But she does talk a lot in these, basically telling you your form etc, and what to watch out for. This is good when your first doing Pilates, but once you do them a few times, you'll be going into position before Kathy does. I actually like Windsors a bit better do to more of a variety. But the talking level is about the same between Windsor and Kathy. So if they are a really good deal, you may pick them up for a little bit extra education, if not just get the Yoga.
Kit