'97s received larger shoulder bolsters on the upper door panels. To accomodate this, Mazda kept the inner door skin flatter by, what appears to me, leaving off a section/layer of material/possible reinforcement of the door. But it also looks to me that the shape of that area is slightly different too.
'97 Top, '96 & earlier Bottom.
So, if you were to try to install '97 door panels into non-'97 doors, they won't fit. Unless you either remove the foam backing in that corner of the door panel or modify it to fit.
With Betty, I just simply do not want to make that minor compromise.
With Rose, when I installed '97 door panels into her, I modified said pieces of foam. I cut out a channel in the foam like so.
I obviously wasn't going to do anything to the door itself to make them fit, that'd be goofy.
But yeah, I like the '97 door panels, I like the larger shoulder bolsters. Some don't, I do.