I actually made this decision yesterday. I picked up a 360 and GOW. All I can say is, do it, you won't regret it GOW has amazing graphics, and it's hella fun.
Target has a special right now, get an Xbox premium system, get a 50 dollar target gift card. Get GOW or a few other titles and get a 10 dollar Target gift card. I checked out 3 times, the 360 first, so I could use the 50 card towards GOW, bought it down to 10 bucks. Then I used the 10 dollar gift card from that and put it towards the VGA connection cable so I can play it in HD on my LCD monitor. Pretty sweet deal.