Than the 16-50 2.8? Are you sure they didn't mean an 18-55? I have very little experience with Sony but given it's a first party 17-55 2.8 sort of lens, judging by the Canikon equivalents that lens should be brilliant, at least sharper than a nifty fifty.
Yeah I wouldn't say they are sharper. The 16-50mm is probably the sharpest lens I've ever owned, you just can't get the wide aperture DOF effect with it which is why I bought the 50mm f1.4.