If I'm eating a genos or pats type steak which is sliced rib eye I am getting provolone..
If it's a chopped type steak like Jim's serves I'm ordering wiz...
A cheesesteak is the only time I will ever eat cheese wiz. There are many, many places that make great cheesesteaks in Philly and each is just a little different.
Now some places use a cheese sauce blend of american and sharp cheese much like chickie and Pete's does with their fries. Steve's prince of steak is one that comes to mind so even though it's a sliced steak I go with the american cheese as it's a really good sauce not just slices of cheese.