Should I start to buy games for my PC instead of Xbox 360?

i dont know. i have call of duty 2 for pc, and i'm starting to play it more and more. i like it because there are a lot of cool maps and mods that you can play. i've seen videos of a mod on cod4 for pc where you can actually play paintball. its crazy-- youtube this ****. the only bad thing is that i cant play on live with my friends anymore. i know that i can like, message them or something like that because of windows live but i liked playing with them. i know that i can always still play with them when i want, but i'm asking if i should buy new games(actually, nvm- CALL OF DUTY GAMES) --i have other games besides call of duty's but i like them on xbox).. let me rephrase my question. Should i buy call of duty- modern warfare 2 for xbox or pc?