The FM3A does lack an interchangeable finders but it does have the K3 split image screen that never blacks out regardless of stopping down, slow lens, multipliers or bellows. (This screen can be used on other compatible bodies.) I don't believe this type of screen is available to any of the F/F2/F3 unless it is third party. I don't know if the other auto focus F's have this available? I have only seen this type of screen on my Canon (new) F1 and not aware if it is available for any other brand/model.
The FM3A also has advantages of higher shutter speeds, higher sync speeds as well as other automation not available in any other MF body as well as full manual functionalities without batteries then any/all Nikons. It's build may arguably be lesser then the F/F2/F3 and certainly it's time of release has possibly relegated it to far less use so we may never know how robust it really is compared to it's earlier siblings. Perhaps what speaks volume for it is the commonly held notion that it cost more to build then what Nikon was able to sell it for and of course that it commands a very good price in the used market.