Socom is more strategy and more realistic.Its more patients then run around going crazy. Socoms controls I feel are better simply cuz they are tight and are fast(to me that is).
Killzone 2 is all out respawn where you have to run around going crazy spraying bullets, rockets, and whatever else or if your CDBS camp by the ammo as you get a massive kill streak even if you lose the game lol. Its fun for a hectic respawn game but it really doesn't take much to be good. You kill a lot of people and get pissed when someone kills you with a rocket it reminds me of resistance but is more loose i.e. not as tight turning, aiming etc...
Socom over Killzone 2 any day.