Fictionvision: With Battlefield 4 coming out in less than a month I'd guess Battlefield 3 will be fairly barren soon. So unless it is really cheap I'd probably pass.
Ki11s0n3: Yeah I was thinking about that as well
BF games cost a lot if you start them at the beginning. The DLC is expensive and the games themselves are expensive. So, if cost is a big factor, get BF3 now and play it for the next few years, then get BF4 Ultimate Edition. If you don't mind paying $60 now and maybe up to $100 on DLC later, then grab BF4 in a short while.
I don't know for certain, but i think a lot of folks can download and play the beta right now if you're itching for some BF action. Or you can get BF1942 free from Origin and tinker with that for the next month.
Crsldmc: Well I can't offer you a balanced opinion since I'm no console gamer, my brothers do but I stick with PC always, I'd recommend you to get it for PC, as Darko said the graphics will be better, and I don't know if this is true but I think console versions have that aiming helper, which as a old school fps gamer is like cheating for me.
Cheers.
No aiming helping on BF3.
But there is a huge gaping difference for performance on BF games on the PC. The PC version supports larger maps (I think) and player numbers (definitely double).