Yeah, but you can formulate a tactic and plan ahead, the AI can't do that. If you see an enemy hide behind a corner you can throw a grenade as well, without some sort of hack the AI can't even do that. You can properly coordinate your units, the AI looks at each one individually and doesn't use teamwork to achive a goal. Speaking of which: the AI has no goal apart from being an obstacle to you (and kill civilians in certain missions), it will never mount a proper attack to drive you off and it won't ever defend chokepoints properly. It is also mostly bad at melee, one of the strongest forms of attack.