Depends upon what and how you shoot as to which model fits you, I think. I bought a 645E and have 3 lenses and had contemplated a change to another model then decided to keep it. My ONLY complaint with the 645E is the inabiliy to change the backs. But I rarely ever have to do that, so why spend the $$$?
On the other hand, if you're doing work that requires you to change out the backs often, the 645E isn't going to make you happy and you should consider the ProTL or the AFD. That's my 2 cents...which is about what my opinion is worth...