ok, I'll run down your points:
1. that's no point, you play games you like and you just own more games you like on the 360. if you were to get BF3 on the Pc, you'd start playing pc more and 360 less.
2. I'm pretty sure PC looks better, but maybe you have an insane TV set or something. still, it's not a point in favor of the 360.
3. so why not get a gamepad for your pc? or better yet, use your 360 controller for you pc (apparently, you can!)
4. get a headset?
5. minor point, can only say if it's a pro if you played it on both and preferred the 360 version.
6. not even going to comment on that one. gamerscore is completely pointless anyway.
the cons are pretty solid as far as I can see, except for the DLC bit. you know windows is owned by microsoft too, right? so either way it's going through them.
7. yes, you probably will. and it's a good way of making sure you didn't just waste a ton of money on something your barely use...
8. again, not really a pro. and it just renders point 5 pointless

9, 10, 11. yep, I pretty much agree with you there
12, 13. I don't think so, it's an anticipated title... but only time will tell.
14. what? I don't think so. besides, like xbox live is filled with good-mannered, mature people...
15. I'm pretty sure PC supports headsets too. but really, how often do you really communicate on xbox live and get anything useful out of it? I don't think it's a very big point.
bottom line: go with the PC version.