I absolutely cringed when I saw those comments about "2k console". Lol jesus

ing christ. You can build a gaming PC for extremely cheap as other people have said here. Even if you factor in mouse , KB, Speakers, etc, it's really not that much more.
It just really depends if you want to buy over-priced gaming hardware and spend 100 bucks on a mouse and another 100 on a keyboard, when in reality both can be acquired for a 10th of the price for something pretty good.
As Apossum pointed out, it's not like your

ing computer just degrades in quality as time goes on. If you build a computer to be at least as powerful as the current gen consoles or more powerful (Which can be done for closely comprable prices, still more expensive but not arm and a leg more), it will STAY that powerful. However, everyone here has to remember PC software moves very fast, like crysis for example. At the least you can play all the games that are multi-platform from consoles, which is most tons of stuff these days, and you can just tone settings down on newer games and they'll still look gorgeous. With self-restraint, you really don't need to upgrade often at all, infact I'm not much for upgrading to begin with.
I'd like to point out I love PC gaming and console gaming, and if I had to choose, I play my consoles more often as many of my favs tend to be on console, unless we're talking FPS and RTS. I just hate a lot of the bull shit myths associate with PC gaming these days.
To the original topic I would choose the PC. You have control flexibility. If you love the controller, you can still use it. If you want to play with KB+Mouse, which is clearly the prefered method by those gaming on PC, you'll have that option too. The PC version is cheaper, has more flexiblity options for hosting (including player size), mods, and is graphically superior. The 360 version I'm sure is going to sell infinitely more copies, and you can just tell by looking at traffic data on sites the track that sort of thing, the 360 version gets FAR more attention. I'm sure the 360 community, will as others have pointed out, have more players at first, maybe even in the long run. I just don't know about that one. I can safely say though, call of duty on PC has always had a pretty big community, you won't have any trouble finding players on the PC version either.
Only way I'd say get the 360 version is if you just don't have the pc for it, It's still fun on 360 in my opinion, I'd just take it on PC if I had the choice to pick between the two.