I am not going to sit here and just yell out my thoughts. I will not list millions of pros and cons however either.
I own both a PS3 and a 360. I personally enjoy my 360 50x better. There are so many more exclusives for the 360 than there are the PS3. I will say that the PS3 games that I own are amazing in their own right, such as Killzone 2, inFamous, LittleBigPlanet, Motorstorm, Metal Gear, etc.
BUT if I were to count all of the PS3 exclusives that were actually really good, I would only need my two hands to keep track of them all. However were I to do the same for the 360 I would have to be using not only my hands and feet, but random objects as well. There are just so many more games to choose from for the 360.
I will admit that it is more expensive to buy the accessories for the 360 like mentioned above with Live, battery packs and what not, but it is well worth it in my opinion. I find the controllers better, the online service blows the PSN out of the water in my opinion and just the general feel of the 360 is much more like a video game console whereas the PS3 feels too busy trying to be a multimedia center. Though for what it is worth, if you are looking for a Blu Ray player, it is very nice.
If you do pick up a 360 however I would suggest getting an Elite, if not the MW2 bundle, but I think that the Elite will suit you just fine. I had the 20GB and it was filled in no time, my 120GB only has like 12 GB left now, but I can make it work, not to mention I have had far too many games.
But yes, I have ranted I am sorry, but in my opinion, someone who faithfully owns and supports both consoles I must say the 360 wins.