I don't own an M1A, I'll say that, but I have shot them.
My uncle has the National Match M1A. I love how it shoots, very classic and authoritative. Accurate too. This model has the Glass Bedded National Match Gas Chamber. It's more accurate, but one terrible downside. If I remember correctly, you can't remove the gas piston to clean it, due to the glass bedding. You will ruin the bedding if you remove it. This is definately not a feature I would want in a combat rifle. Other than that, it is a great gun.
The other one that I have shot is the Socom 16. Love it!
Absolutely sweet to shoot. Smooth, smooth, smooth. I almost want to say that it has less recoil than my AR. Well, it is less sharp, less abrupt. Probably the same, amount of movement, but is slower and smoother. I do very much like this rifle. I DO NOT, however, care for the Socom II. The picatinny forend on the SOCOM II is awkward, heavy, and uneeded
My vote is for the M1A Scout with a synthetic stock. This is
a good middle ground between the two. It is lighter and easier to move in tight places than the Standard, but has a little more velocity and accuracy due to a longer barrel than the Socom.