Kali, Slim in 6 is nothing like P90x, nor is Power 90 really. (Sin6 is the most beginner/intermediate of the Beach Body workouts).
I have P90X and LOVE it! By far the most effective upper body workouts I have used, period! The rotation is put together so well...and obviously well-thought-out before the workouts were even created. The cardio is less intense (for a purpose, P90X is a strength/muscle-buiding program, and the cardio it includes works well in the system).
The whole system has an effective variety of workouts: upper body strength, lower body (using light weights or no weight), plyometrics (not the "jump as high as you can" type for most moves, but a type that seems more effective tome), yoga/stretching, a focused core workout (that really works the entire core, and not just the abs, like some supposedly "core" workouts), kickboxing, an effective ab workout (even if you end up skipping it sometimes, like I did!).
I was able to do the entire 90-day rotation without being sick of it(for me, it took about 105 days, because I added some rest days or some extra cardio from time to time). And usually, I get tired of doing the same workouts pretty quickly. The results were what kept me going.
I also really like the way the weight workouts are organized. It's not the old, stale, "work X body part to exhaustion before going on" set-up, but either push-pull (a chest exercise followed by a back exercise, then repeat, then take an active rest) or circuit (one exercise for shoulders, then biceps, then triceps, then repeat, then take active rest).
The only supplement I needed was heavier lower body work (my butt doesn't stay "up" if I don't get it!), like adding in some sets of heavy squats with the leg workout. There is also enough recovery (within workouts, between workouts, and as a designated "recovery week") to allow the body to build and repair. And Tony never says (that I recall) "hurry, hurry, hurry," which I don't like to do when working with weights.
I got in the best shape I've ever been from P90X. I finally got a "two pack" (which was on it's way to becoming a "four pack!"). My core was much stronger (after doing a few weeks of P90X, I tried pikes on the ball--which I was never able to do previously---and I could do them! And there aren't even any pikes in P90X!) My upper body definition was improved. I was much stronger (I was able to increase weights and/or reps with almost every workout.
Hmm...I should break out the P90X DVD's again!
Some people say they find the style of P90X "too macho," because Tony is a bit of a show-off at times. The sets are functional, and look like a gym, not "pretty" and decorative. No matching outfits on the exercisers and, (except for Tony!) no obvious make-up. I actually like it!
