Here's my mind about it so far:
PC
~Better graphics (Not sure about this one)
~Headset
~Moddability (Is this even an option?)
~More buttons for hotkeying
BUT my computer can be finicky sometimes, and some games don't play on it due to a blackscreen bug. I think it's failing video hardware.
Xbox
~Easy 'flow' of movement with a stick
~Friends play it
So neither side really has a large advantage over the other. Is there anything I'm missing?