Couple of points, while the PS3 outputs at 720p (1280x720) a lot of the more taxing games are internally rendered at lower resolutions, sometimes 1024x576 and then scaled up to 720p, because the GPU is a limiting factor, as is the case with the 360.
Also regarding the difference between the SPUs and the main ALU core on the Cell, the biggest difference is not just integer versus FP, it's that the SPUs are very poor at branching and are therefore not good for running any kind of user input driven general purpose code, or evaluating AI and so on.
Rendering and other calculation heavy code that do not require any "IF x do something, otherwise do something else" type of code are much more suited for SPUs.
Also regarding the difference between the SPUs and the main ALU core on the Cell, the biggest difference is not just integer versus FP, it's that the SPUs are very poor at branching and are therefore not good for running any kind of user input driven general purpose code, or evaluating AI and so on.
Rendering and other calculation heavy code that do not require any "IF x do something, otherwise do something else" type of code are much more suited for SPUs.