I hated PES when I played it, I though it was one of the worst football games ever. And I do quite like FIFA so that's where my vote lies.
Yea, you can also play FIFA online without cd key although you need one lol
PES all the way, Become A Legend mode is far more superior to FIFA's Be A Pro mode.
Of course Fifa, not just because it has EVERY team out there and not just because you don't have to guess that Man Red = Manchester Untied (lol) but also the Gameplay is way better with better controls.
If you bothered to search the web, you don't need to guess anything except which formation you play with West Ham against Robben-ized Real Madrid
Also, anyone who says FIFA is better, well has no reason to do so.
I saw controls were mentioned, they can be changed, graphics, well FIFA doesn't even have an argument on graphics if you're on the PC.