I am doing a mixture of both and am getting almost as fit as when I used to go jogging two years ago (and I'm too heavy for that at the mo)
The Turbo Jam is absolutely hard work but the most fun workout you'll ever have, Chalene the instructor is a FANTASTIC motivator; whereas Slim in 6 really does 'bust your booty' (ouch) but you know it's working. It's slightly more boring but sometimes you need boring to get even more results.
Anyone else doing either of these?
Oops - just realised there is a thread on this in the Fitness Video section.
Please ignore