hmmm i dun quite get ur question. Are u comparing AF on subject eye, difference between AF-S and AF-C?
If tat is ur question, then theorectically, should be able to achieve the same focus on subject be it af-s or af-c... But in practical is diff story
u might not get the same focus dependin on ur settings.
by default, in AF-S, u can snap a pic only when it's in focus.
in AF-C, u can snap a pic even when subject is not in focus