In keeping with the "no question is a stupid question", well, here goes:
Everything I read leads me to understand that an EF lens on a crop body is going to perform great because framing is in the center of the glass, and the outer egdes of the lens, which are normally the problem areas, are not used. With a much more vast array of EF lenses available, it seems you could achieve just about any lens specific desire or requirement on a crop body, and theoretically have better quality. It appears to me that FF is coming into the consumer price range, and crop bodies could soon be considered more of a specialty type camera, for those who want "the reach" as it is referred to. And you get better "reach" on a crop body with an EF lens. So why would I even want an EF-S lens?