Why does phenom perform better than an intel quad at high resolution in Lost Planet?

[gallag]

now you can get an intel cpu clocked 4ghz and get a phenom clocked at 3ghz. the intel will have a higher fps but does it mean its better? if you actually look at the game instead of the fps you will notice that the amd system runs a lot smoother even tho the fps is lower.

Is fps not what makes a game smooth? I can see the argument in saying windows is smoother etc but in a game does fps not define smoothness?