It's a bit strange to be asking strangers to tell you which of your cameras (that you already own) you should keep. If you've shot with both cameras, you should have formed some kind of opinion on them, and should already have some kind of preference...

The choice will also depend on what you use the camera for (sports, weekend trips with family, bugs and flowers - macro shots, expeditions to the Amazonas or to the North Pole, etc...) - which you did not say in your question.

So, it's purely a personal preference.

However, putting all that aside, here's what I think about them (and I've used both).

FM is a no-nonsense purely mechanical camera, with batteries used only for metering and nothing else. If the battery dies on you, you lose light meter and can keep on shooting. FM is also a lighter camera (590g, if I'm not mistaken). It does not have auto-exposure!
Still, it's a very rugged camera, which will keep on working in all kinds of conditions, even without batteries or in very cold climates (the reason for North Pole reference above...).

EL2, on the other hand, depends on battery to function, and has only one "mechanical" shutter speed when battery is empty: 1/90 sec (if I remember correctly). No battery, no shooting... except on 1/90 sec. It's also a much heavier camera (880g, according to specifications found on the Internet... don't feel like weighing them right now...).

EL2 is definitely a more advanced camera: it has a good auto-exposure mode, has mirror lock-up (important if you shoot bugs and flowers and other macro kind of stuff - for me it was inconsequential), better range of shutter speeds (sometimes quite important)...

I really don't know - and I think I'd keep both That's what I did with mine - I still have both, although I don't use them much. More of a sentimental value than everyday shooters, though (my eyesight is not what it used to be...).