PS3 is superior
Cell processor can handle gfx instruction You can notice that with PS3 exclusive games like Killzone, God of war3 etc ...
PS3 has 8 SPE out of which 6 can be used and all post processing effect are handle by them. Since god of war3 they managed to do even aa on it. So RSX can do more things. Moreover streaming data from blu-ray disk give PS3 advantage too. John Carmack said PS3 blu-ray gives them advantage in texture streaming. PS3 dev has also undergone lots of changes and now devs are able to use it more properly. Memory is also improved since PS3 was released: