How does the Sony 16-50 f2.8 compare IQ wise to the Sony 35 f1.8?

I use the 16-50/2.8 and 35/1.8 in the studio, and the I find that the 16-50 gets sharper results (centre frame) then the f35/1.8.

It ifs only at the corners do I think the 35 is a little better, but since it can't quite get pixel level sharpness in centre, I see it as quite noticeably inferior for detail work.it also seems to have less contrast..

I've done a couple of weddings with both lenses, and this mirrored my studio results..

It's a shame the 16-50 is a bit soft in the corners, but with such crisp detail in centre, I use this in place of my cheaper primes purely because it really delivers far more often then any other lens I own, and the zoom range is very flexible, not to mention the SSM and the build quality.

E.G. f/2.8 and f/3.5 1:1 on an A77..