Note: I own a Garand and a FAL.  My dad owns a M-14 and a HK-93.   I've fired the G-3 however.
M1 - Probably the most accurate and the best sites.  The 8 round clip is a pain, both to load and to carry.  Too heavy compared to the others.
M-14 -  Suffers from weight.  Nothing really wrong with it, just that the others are better.  And it's just brutal on full-auto.
G-3 -  I never liked the HK's that much.  I don't like the bolt handle being up front and I'm not that big of a fan of the rear sight.  I have friends who are FLEO's and they swear by them.  Dunno, they just never did anything for me.
FN-FAL - The cream of the crop in my opinion.  I've fired thousands of rounds through mine and others and cannot remember a single jam.  Simple to clean.  Decent weight, not too light to aim and not to heavy to carry.  I prefer the .308 to the .223.  I also like the simplicity of the Accurate out to 300 yards with the flip-up rear-sight.  Can easily shoot farther with a scope, but you probably don't need it in most combat situations.  Anyways, I could go on, but that would just be cumulative  
