Bro I'm debating getting a new Xbox to go with my PS3...what do you think? 
I now have both after just having the 360 since it launched. it depends on what you what it to do. If you are a hardcore gamer and play online games xbox live is the better system but the ps3 version is free. the basic 360 is cheaper up front. But buying live is like 40 bucks a year, which is almost the price of a game. The slim is nice and is mostly quiet, 360 is a little loud.
360 has netflix streaming on it, which is awesome.
Plus you can stream movies and music easy form a PC.
Both systems, (old PS3 and 360) have had hardware problems tho the 360 is far worst.
The 360 controller is better, but there is a 3rd party controller the feels like the 360 is out now for the ps3.
i would also see if there are any games out for the 360 like gears of war, that you want. The 360 has more ram so the graphics are better. Plus it is easier to program, which also helps the game's performance.
If you got a 1080p TV, blu-ray is great. But not as convenient as the 360s netflixs and live download model. That said 300 bucks is a great price for a ps3, my bro bought his for 600 bucks at launched and was having the drive problems that have be plaguing ps3s. HE really big into blu-rays too.
