I've used both. As far as losing weight.... that has a lot more to do with your eating, not the exercise. Like, 80% more. So unless you track your food (weighing/ measuring out your portions, etc) you won't just automatically lose weight while doing either dvd.
As for firming up.... Leslie Sansone is light aerobics so it's not going to give you the toning that strength training will. Personally.... I've never lost a bunch of inches doing her stuff. It's a way to get a little cardio in, if the weather's bad and I can't walk outside. A lot of her stuff is available on youtube, so you can do a workout without buying a dvd.
Jillian Michaels includes some work with weights on the dvds. It's fast paced and I like it because it seems like it's over quicker. But she includes some higher-impact stuff for the aerobic portions, and I've got one bum knee which limits the jumping around I can do. It's similar to circuit training, so you could search either on Spark or youtube for a workout and try a few to see if you like that style, before buying a dvd.
I've had good results with the "firming up" just doing free videos here on Spark. There's a Jumpstart January (or January Jumpstart, I don't remember) challenge that gives you a video to do every day. One day it's core, one day it's lower body, one day it's upper body. Each video is about 10 minutes long.
Ruth in Cookeville, TN Central Time Zone
Promise me you'll always remember: You're braver than you believe, and stronger than you seem, and smarter than you think - Christopher Robin to Pooh
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