Crysis 2 didn't have a very good framerate on the ps3. It stayed in the lower 20s. But thats ps3 games in general. The 360 had the grain glitch issue. I suffered it. But I doubt crysis 3 has it. So... you start with the most powerful and move down. Not a powerful enough quad core pc? Get the triple core 360. 360 red ring? Get the single core ps3.
I'd get it on the 360 if I was you, it comes out darker and sharper on the 360, at least it did in Cry 2, but in the PS3 this year they did a great job. One way you can tell is off map way more detail. Either way you can't go wrong. The other thing to consider is a gazillion people have xboxes and the PS3 version has like 50 people online period, that's the most dissapointing thing about Crysis 3 I dont get it cuz it's a better game than COD series IMO. I only own a PS3 but I assume the 360 has way more peeps online.