Both. BF3 looks amazing, fresh, innovative, a true sequel. The Frostbite 2.0 engine is breathtakingly beautiful, even for PS3. The character animation is the best I've ever seen in a video game. Multiplayer is gonna be off the chain for that, I can tell based off the Gamescom BF3 trailer. Destruction, 64-player warfare (if you're on PC) vehicular combat, emphasis on teamwork, and huge maps... how could anyone not be at least somewhat interested in this game? Battlelog is basically Facebook for shooters, and to top it off, it's completely free *cough*CoD:Elite*cough*. BF3 will be what CoD4 was for first-person shooters back in 2007.
MW3's multiplayer shows a much needed revamping after the stench that was Black Ops (with the new classes), and Spec Ops/Survival mode looks like a real treat, especially since it's being treated like the online multiplayer modes now with progression, killstreaks, ranking, etc. It's basically what MW2 should have been. The campaign will be fun and over-the-top as usual, and will be the end of the MW trilogy, making it a must buy, IMO. Although the graphics just look like MW2.5, I still think there's much fun to be had with this eighth installment.