Personally, I liked MW3 better than BO2. Guns felt & looked better, & the maps had more variety. That's just my opinion, though.
With COD: Ghost coming out soon, you should probably just wait for it to come out. I'd preorder it now, if I were you ('Less you plan on getting some special edition). No real point in getting BO2 if the other game is going to be released in the near future. It'll also probably get boring after a while unless you get a map pack/season pass too, & that just adds more to the price tag.
Just my two cents.