One of the more stupid arguments coming from 360 players, is that "The PS3 just isn't fun. When I go online I don't feel like I can communicate with anyone." This argument gets me angry, because when they say this, they do not even specify what they mean. Okay if they said something like "Oh I really like the party chat feature, and the PS3 doesn't have it." then it wouldn't be so bad, but when you make an argument with no basis that gets me angry. As for PS3 arguments I hate, is that PSN is free. While I actually do agree PSN and XBL are basically equivalent, people on PS3 will ONLY use that argument in an already stupid discussion.
It is a matter of preference. I think the three main factors that affect it most are library, controller, and what previous generation system you had. If you had an Xbox, you were obviously going to buy an Xbox 360, so therefore you prefer it. The library can make or break a system (although most big ticket games are cross platform nowadays.) The controller is also a surprisingly big factor. I personally hate the 360 controller (again, most likely because I have always had Playstation so the feel of that controller is just engraved in my muscle memory), but some people on 360 swear that the PS3 will break in half the second they pick it up. I will throw in my own thoughts on this from personal experience. The PS3 controller is basically indestructible regarding anything you could do to it while gaming lol. A friend of mine abuses his, as in throws it across the room on a daily basis and hits it on the wooden arm of his chair every day. It still largely functions with the exception of a bit of a sticky left analog stick, which is probably related to something that got into the controller itself.
I think the argument between any console is stupid, PS3 v 360 v PC. Just play what you have and stop bitching, because the only purpose of the argument is so that one side can finally feel like they won, and say that they spent their 300$ on a better product.