Gatorade's effective if you're gonna be doing long strenous exercise or if you're in the hot sun for long periods of time eg. cricket players. I can't give a scientific explanation but apparantly it's better than water if you're doing this. But don't replace water with gatorade 24/7!
There are a bunch of articles online about it so do a search and see what you find. I think the general consensus was that it's mainly good for helping you drink more WATER, and therefore keeping you hydrated. It's way easier to chug down a bottle of gatorade than water, so in that sense you'll be more hydrated, but other than that most studies show that it does very little.