How good is the XBOX 360?

I REALLY wanted to get a PS3 so my brother and me can play MW2 at the same time but I heard you cant play at the same time because you will be using up the same ports and it will disconnect you. Is that true? Does the XBOX use different ports? If so is it worth it to buy it for $299 and then get mw2 with an HDMI cord? How much will it cost to play online with other people? I need pros and cons.