The tamron was always sharper than the Siggy in tests but the 17-50 VC is not a patch on the non VC version.
I consider the 17-50 VC to be an anomaly, the 24-70 VC for instance is actually better than the Mk 1 Canon 24-70 f/2.8L and a good grand less than the Mk2 (Which i concede is likely better but still...)




