Battlefield 3 VS Assassin's Creed Revelations?

Before I start I just want to let you know this is more like a general question, rather than a problem and I want to know the opinion of most hardcore gamers out there. I have been looking forward to Assassin's Creed Revelations ALL YEAR, and since I currently own all AC PC versions (From AC1 to Brotherhood) I considered buying the collectors edition. But recently one of my friends showed me Battlefield 3. He pre-ordered the limited edition and I was able to check out some single player on his PC. When I went back home I torrented BF3 just to get a general idea of the game and to my surprise (considering I am actually a COD fan) the game was truly amazing. So far this is the only game on which I have been able to test out the true power of my 6970, running the game on Ultra with maximum motion blur and vsync turned on at an astonishingly impressive 45-30 FPS. I played the first few missions and now I really want to play the multiplayer as well. The problem is, if I buy BF3 I will be in no financial position to buy Assassin's Creed Revelations when it is released. This is a really weird problem because suddenly those "boring overused FPS's" seem interesting again and the unique AC series suddenly doesn't feel as awesome as it did during the first few showcase trailers.