I have had both lenses on crop and FF bodies. Picture quality in respect of sharpness is outstanding in both lenses. Even the build quality of the EF-S 17-55 is very good - it's not weather sealed like the 24-70L, but you cannot fully utilize this feature with any other body than a 1D anyway.


Also, don't forget the IS - it makes the EF-S 17-55 even more desirable in comparison to the 24-70. Especially since you want to shoot indoors a lot. For a crop body you want to have the wide angle of the 17mm - don't bother looking at the 24-70 anymore :-)


I only fear that once you start using the 2.8 glass you will want to upgrade your 70-200 as well ...


AxelB