the plain prism commands a higher price for a reason.
the metered head is purely functional; that is to say that it looks like a big growth on top of your camera but it allowed you to have in camera metering. at the time, this was fine. these days though, you can get any number of cameras with more elegant solutions; so what makes the Nikon F2 a good camera today (build quality, simplicity, etc) has caused a shift in what people are really looking for.
the F2 is a big camera.
the fm series are fine but they have small finders and poor coverage compared to some Olympus and Pentax offerings. I'd stick with the real pro offerings as they are so cheap these days that it doesnt make much of a big difference.
my picks for basic, reliable, inexpensive cameras:
big cameras: Nikon F, Canon new F1
small cameras: Olympus OM-1, Pentax LX, Konica Autoreflex T3
why do you need an SLR? if you want to do macro, I would recommend Olympus since the stuff other than lenses (bellows, ring flashes, true macro lenses, screens, etc.) are plentiful and not too expensive.
if you're interested in spending some real money I would point you towards Nikon and the ZF lenses.
p.s. isnt one of the big selling points of an SLR accurate framing? fm2 has 93% coverage...
