Another issue I feel is important is the viewfinder. The FE has a rather dim and small one compared to the F90X. This is a pain when shooting under dark conditions. I have given up macro with reversed lenses with the FE because of that.
The FE2, FM2n and FM3A should be better, I don't know since I havn't tried them.
As to the F90X it works great with AI(S) lenses which I find easy to focus on the screen.