I haven't used Norton, but their products are considered to be pretty high up there. Partition magic, however, seriously f***s with your drive. It can report errors if you have linux partitions (and fix them in such a way that you'll never see linux again), and I've heard (so don't rely on this), that it messes with the boot sector too. It's one of those "wizard-point-and-click-shiny-buttons-user-friendly" packages. After trying it once, I wouldn't recommend it.
Vlad