If you wear glasses, you'll prefer the F3HP over the FE/FM-finders. The only advantage of the FM-series is the all-mechanical shutter (I had my F3HP die from battery failure on a trip to Cuba a few years ago. Finding suitable batteries there wasn't exactly easy!)
Uncle Bill: The F4/F5 also had interchangeable finders but IIRC, the F6 does not. That is one hell of a camera anyway...