I've never owned a pro zoom, but the biggest difference I've noticed between lenses is when I compare my primes to my consumer zooms. All of my primes, even my budget Minolta Celtic from the 70s, are better than my best zoom. The wide primes are much better at controlling distortion and that is noticeable at any print size. But there is also a less tangible aspect to these differences. My best primes have a signature that makes the photos seem to glow...for lack of a better description. Maybe there are technical terms to describe it, but it's more than just sharpness. I suspect some of the pro zooms are similar. It's unfortunate that you have to pay for all the "professional" bells and whistles to get the best image quality. One of the reasons why I buy old used film gear.

Paul