We can talk 'accuracy' of these rifles but they all shoot bad with bad ammo.
The M1A I had would shoot an honest 1 inch group at 100 with iron sights. With a scope that opened up to 2-3 inches. I went thru 3 mounts, including the very best available, and that is what the rifle shot. The front sight leaned to about the 1.30 position and the 1 inch group would move depending on whether the front sight was vertical or the rifle was vertical. It had a terrific trigger and never failed with good ammo.
I watched a guy shoot a HK91 with the good (HK) mount and a good scope at 100. It shot 1/2 MOA at 100. I tried to buy that rifle but no. The ergonomics don't fit me too well but I expect it would work ok...
I have shot 5 or 6 FALs and that is a **** shoot. The Metric guns out shoot the inch guns ( to be fair the inch guns were all Bitsis.... A bit of this and a bit of that as the Brits say). Except for the grip, I like the inch controls better. All the inch guns ( well worn and who put them together?) shot 4 to 6 moa. All the metric guns shot< 2.25 moa. Find ammo they like and most of the metric guns will stay under 2 moa. I watched one shoot into one little hole (< .4 moa)(5 shots). Was it a fluke? Maybe...probably... but it did do it.
Scope mounting on an M1A didn't destroy the balance or the feel of the rifle. A scope on a FAL destroys the balance and feel of the rifle... at least to me...
I don't own one but I think the current crop of AR rifles in 308 are the best of all of these. I didn't say I liked it the best... But if you want to build/work on/ modify your rifle to your specs....they are the way to go Just my opinion...YMMV