i have only done a few quick sessions with pro tools (and never at the helm) but i own logic, so i wont be a great source, but i can tell you very quickly that they are pretty different.
pro tools is more oriented to replicate a standard studio experience, logic is much more free form--- created more for music production and less for recording if you catch my drift. better midi, easier perhaps for doing soundtrack sort of stuff.
i dont think one or the other has a particular advantage in terms of sound quality, but the hardware in pro tools, while expensive, makes it a bit more robust. but that robustitude comes at the expense of flexibility.
logic is a fuck of a lot cheaper. made for a different market... for the $500 student discount rate you get the full version of logic with the full suite of plugs (and they are pretty f-ing good). throw a $500 hardware card with that and you are off and running. a good deal.
you can get that sort of thing going at that price with pro tools LE, but LE comes with a bunch of limitations that puts it in a different class from logic.
