Lag free is not the only thing that makes a good online system.
PS3's online doesn't support any type of real unified system. No PS3 Online functionalities are intergrated into the games....meaning, they each use their own system. You have to log all the way out of a game, to the main menu to see if your friends are on. If you send them an invite, you have to hope they're playing the same game....or else they won't get it. But there's no way for you to know what they're doing....just that they're online. But even if you get an invite...you can't just accept it. You have to actually go find the game and join...it's more like a note that your friends are playing this certain game. This among other things is a HUGE HUGE HUGE hurdle they have to overcome.
On the 360 (as a lot of you know) the online, and community features are done very well. All the friends lists are intergrated into one full system on every game. You can see who is online, and what they're doing at anytime. You can send invites to anyone at anytime, and it will jump them right to your lobby. New friends you make in games, will be transferred to your friendsd list, there's a ratings system that carries over, there's match making, etc., etc.