The best thing about CamelBaks (and similar products) is that they get you to take small sips frequently. This is the most ideal as you're only replacing the water you are sweating and only when you need to. With water bottles you (well, I know I do this at least) typically don't drink as often, and take large gulps when you do. The problem with this is that it doesn't hydrate you as well, and it makes you pee.