The FE and FE2 have been my favorite bodies for a long time (although I should include all of the EL family as they have the same attribute). The analog shutter speed scale in the viewfinder is a very easy to use gauge of the number of stops of over or under exposure, and I no longer need to look directly at in order to know if my shutter speed is fast enough. Shooting any subjects that move, while handholding the camera benefits me with such information always available. If I use any other body, I constantly have to stop and think in order to judge the effect of the lights and numerals on the exposure. While the FM is easy to understand if the shot will be over or under exposed, it doesn't tell me by how many stops.
There are a couple of other differences, one of which you have identified regarding the shutter release lock, but the viewfinder exposure information is paramount for the way I shoot.
I do agree that if you're familiar with and enjoy using the FM2, you will be better off standardizing on it and not losing that 1 second of time recognizing which body is in front of you when you raise it to shoot.