I'm considering buying one of the beachbody series also but I'm thinking of going right past the slim in 6 and Power 90 and going for P90x. Because I've been doing the FIRM for about a year with awesome results. I highly reccommend the FIRM but I can't say whether Slim in 6 is better or not I'm thinking resultswise it may be comparable. My only caution with the Firm would be knee"wise", if you have any problems because there is a lot of stepping up and down on a box.

I read Power 90 workouts are not that long so if you want something shorter timewise that might be a good one. It also builds muscle whereas Slim in 6 doesn't.

I'm wondering about the beachbody series too so I hope you get a lot of answers to your question. I posted one about P90x last night.

Good Luck!
Jenny