Might as welll add the FAL:
Cheap mags, cheap available parts. Lot's of good quality make's out there in clones.
Don't like the regular grip, sights suck, it's overall a thin gun with a big stupid knob sticking out from teh op rod, but I'm getting a folding one for that :smile:
I don't like an adjustable gas system, since the AR-10, HK91, and M-1A all seem to do quite well without it. Most times, you'll set the gas setting and never touch it again.
Oh, and the bi-pods for the HK and FAL are definetly a plus for a light portable weapon. For more match grade stuff, they don't take other bipods well.
I don't really like the feel of M-1a's, and haven't shot one, so I'll refrain from commenting there.