Regardless which lens, it also makes quite the difference once you start using the best parts of it. I had some issues with the Tam's performance but a lot had to do with shooting it all through the range at any aperture that light allowed me.
Since I quit doing that and only use the best parts of the lens and select which the light allows, it really shows in my shots. It's a compromise in which I pay the price in flexibility to gain quality but it's one I gladly pay.