Fitprime and Slim Series are both very different from Cathe, and from readiing posts on videofitness.com, I've found that people rate them at varying levels of intensity.
Here are my observations:
Fitprime alternates weight work with short cardio moves, sometimes done with light weights. Many of the moves are quite novel (some say "weird," others say "innovative.") For example, you can do push-ups with one hand on a med ball and the other on a tall step, or squats that emphasize one leg. I find them to be intense, but in a different way from a Cathe tape. If you want to try them out, I'd suggest starting with "Strong Bear" (they also tend to have kind of whacky names. When I think of "Strong Bear," I wonder if there is a "sits" in the woods move!) which is one of the most liked ones.
I find that Slim Series is intense, but in a cumulative way. When you follow one of the rotations, you work out almost daily, using light weights (the instructors uses 3, 5 and 8 pounds) and resistance bands. There are also plyometrics and some light very low impact cardio interspersed with the weight work. When I did a two-week Slim Series rotation, I felt that my legs were "tighter" than previously, and I began to see more definition in my abs. I did, however, miss heavy upper body work, so I threw in a PUB workout. If you want to try Slim Series without commiting to all 6 tapes, I'd suggest trying the "Keep it Up" DVD, which contains a 40 minute workout similar to SS as well as an ab workout and a stretch workout. "Keep it Up" is kind of an "unofficial" part of the Slim Series, as it was created as a follow-up to "Slim in Six." The SlimSeries workouts themselves are and hour long, except for two that are about 80 minutes long.
One big bad point about Slim Series, IMO, is that the music is used over and over and over again throughout the series, and it's not that great. Fortunately, there is a "no music" option, which I've really enjoyed.
