Of the .308s you've mentioned, I prefer the M1A variants, but I'm biased as I have a significant investment in one of my own — a "Loaded" model with full length stock and barrel. That said, my preference is based entirely on having lusted after one for 40 years, and only fairly recently (last November) having satisfied that lust. I could easily be very happy with an AR10 variant as well. At the time that I bought the Springfield, there was an AR10 and an FNAR bull barrel on the rack right next to it. I actually gave all three rifles a look-see, but my heart was in the M1A — oh, and in keeping with all the latest rage, it's a gas piston design too.
But if I were going to buy a second .308 semi-auto rifle today, it would be an AR10 variant, with or without gas piston, rather than the FNAR.The M1A is a great rifle. If topped with a good scope, it easily meets your 1 MOA requirement. Depending on load, it is capable of better than that, but the average is right at 1 MOA. My groups, with all ammo fired to date, have been in the .5" to 1.5" range, depending on the cartridge fired. It tends to prefer 168 grain SMKs to anything else, although I had outstanding results with both Black Hills Gold 168 grain A-MAXs and the Hornady 168 grain HPBT Match. Best groups with those cartridges was a rare .5", and not with any great consistency. For hunting applications, it will shoot a best of .75 MOA using 165 grain Federal Fusion, and based on that bullet weight's performance, I've also purchased some Nosler Custom 165 grain Partitions I want to try; but that stuff is pretty pricey, so I don't plan on feeding her a steady diet of it.
Other things to think about in making your decision...
Weight: LMT doesn't list the weight of their rifle on their website, but a DPMS LR-308 weighs in at 11.2 lbs. empty, while a full sized M1A weighs in at 9.5 lbs. I imagine that the Scout/SOCOM versions are lighter yet due to their shorter lengths. If you're going to be humping a rifle in the field, that's a significant weight difference to consider.
Reliability: My M1A never jams. Not ever. But, it did have a critical part failure. Somewhere into the first 100 rounds fired, it broke off one of the two hammer hooks. It continued to function, but it would have been only a matter of time until the other hook broke, rendering the rifle useless. It is a MIM part — as are a couple of other items — and after browsing another board, it seems that this is not that uncommon of a failure. It doesn't happen to everybody, but it does happen to some. That said, Springfield Armory's customer service department is awesome. I had to ship the fire control group back to them (it pops right out the rifle in about 30 seconds), but they paid for 2nd Day Air FedEx both ways and turned the repair job around as soon as they got it. I had the repaired fire control group back in my hands about 8 days after I sent it to them. Also, SA replaced the broken hammer with a forged piece at my request and without disputing it, so I don't anticipate that ever happening again. I have nothing but good things to say about their customer service. I have been advised by other M1A owners to replace my operating rod with a forged piece also, as the original is MIM also and has been known to fail. So I'll be keeping my eyes peeled for one at the gun shows.
Optics: Unless you buy a Scout or SOCOM model, the M1A does not come optics-ready. You have to buy a scope mount for it so as to have a rail on which to mount the rings. Installation of the scope mount is not impossible for a person of average mechanical skill — I mounted mine (from Sadlak) without too much trouble — but it does require some measuring and fiddling to get it right. That said, the iron sights that come on the M1A are superb, and are adjustable out to "that dot is a man?" distances.
Other: The M1A stock was designed for use of iron sights located just above the bore — not 2" higher up like on the AR. In that configuration, the rifle is actually quite comfortable and easy to shoot well. Anyone who has ever fired a Garand would feel right at home. However, because of the downward angle of the buttstock, when you put on a scope mount and even low profile rings on top of that, the scope is mounted too high to get a good cheek weld on the stock. This requires the addition of a cheek rest of some kind. Scoping a flat topped AR doesn't present that same problem because the scope is nearly the same height as the irons in the carry handle on an A1 variant, and because the buttstock comes straight back from the receiver and is inline with the bore, instead of angling downward like on the Springfield. Consequently, the cheek weld height is not as far off. I used a Karsten's Adjustable Cheek Rest for my M1A, which provides enough height to make the scope work right and can be adjusted all the way down for use with the iron sights, but that required drilling a couple of holes through the stock to mount it. (It should be mentioned that most of the M1A scope mounting systems will still allow you to use the irons if you want to, without requiring you to remove the mount.) Having never sighted through an optics mounted Scout or SOCOM model, I couldn't tell you if the problem is the same as on the full sized rifle, but looking at the picture posted above, it looks to me like it might be.
I hope this information helps you to arrive at a decision. I wouldn't let these things deter you if you really want an M1A, and knowing what I know today, I would still buy that rifle and not the other two (AR10 and FNAR) that were on the shelf that day. But the early part of my ownership experience would have been less complicated if I knew these things in advance instead of having to sort of figure it all out on my own. Still... no regrets, and I love my M1A more than either of my ARs.