I have both books (South Beach and Supercharged). Supercharged has some more up to date information and also has an exercise regimen detailed in it. If you are just starting with exercise it is helpful. If you already have an exercise regimen you probably won't use it.
I've got the SuperCharged book and the main difference is the exercise program... If you have any other editions of the book, you don't need the new one IMO... you can get the changes to program (the changes in dairy during Phase 1 since the first book for example) though the Stickies on the FAQ on this board.
Dr A recommends interval cardio and strength training in SC... Although he has a specific training program, IMO you can probably come up with something that is a combination of those 2 things that works equally as well as what he recommends.
The only reason we bought SuperCharged is that we couldn't find the book we had from when we were on SB before.. I have a vague recollection of lending it to someone who asked about the program because we were doing so well, but I can't remember who it was....