mw2 cuz its just alot kooler and if you think killsteaks are overpowered then you MIGHT just be lazy and not wanna whip out a stinger and shoot the b*tch killstreak down
MW1 was still very much like most MP games at the times. I believe that MW2 took what made it special, Killstreaks and perks, and took it to another level making it more unique and better.
It does have the worst respawn system ever created and those shitty deathstreaks.