Andy Roddick forehand in slow motion:
http://youtube.com/watch?v=iAKrOD06HWU
Roddick looks until he can look no longer due to his technique & stroke. Western grip relies on a lot of upper body rotation as we see in the clip. He looks until he can't look no longer and the ball has slowed down considerably. As well as Roddick goes from a low to high motion as we see. It's harder to hit the center of a racquet with a low to high motion as such.
While Roger Federer technique and stroke are more with open shoulders. Which allow him to do what he does (look at the ball & contact point). He swings more on a level plane so it's easier to hit the sweetspot more often although he doesn't hit the sweet spot a lot of the times.
Federer even though he's #1 in the world and has some of the best strokes does shank a lot of the balls when he deals with certain people or on certain courts (clay).
Roger Federer's strokes in slow motion:
http://youtube.com/watch?v=9t3auwuvJNk
Those are pretty biased pictures since that's one out of the many they hit. In a game they do hit well over 500 or so shots and a good portion are not hit perfectly on the sweet spot. A lot are not within the sweetspot range, rather a lot are outside of the sweetspot range.
What seperates Federer from a lot of people is his footwork and his preparedness. A lot of people are scrambling for the ball while Federer is not. Federer is a lot of the times prepared for the shot. As they always say on Television it seems like Federer has so much more time to prepare and hit the ball compared to other players.
As I've always said and said before. Any pro tennis player if they're prepared and setup, they will hit precise shots and hit within the sweetspot range. If not, it's very difficult to (scrambling) even for Federer; on the run he shanks balls and hits way outside of the sweetspot as shown in many videos and even in the slow motion video I uploaded.
Racquet and technique has little to do with it, but mostly footwork and preparedness. And this is clear to see.