i have both games and both suck.
PES 2010 playes more like a ps2 game.
FIFA 10 has the most ridiculous rubberband AI ever.
I used to play FIFA 09 every day online, it was an awesome game.
but fifa 10 sucks. it uses a ridiculous handicapping system and it uses it ONLINE!!
you can forget playing fifa 10 online, it has only little to do with skill anymore.
Anyway i bought MW2 and its awesome! (i am on 360)