The literature that comes with an M1A from Springfield says their rifles are cleared to shoot all Nato 7.62 ammo and all .308 ammo except the High Energy stuff.
As I understand it, the M1 should be loaded to about 2700 fps. with 150 gr. bullets. That means if there is any difference, it would be with the .308 ammo.
As far as accuracy is concerned, both of my rack grade M1A's shoot best with milder handloads. The Squad Scout puts four into 1 MOA with 46 grs. of TAC and any good 125-130 gr. bullet. The Scom 16 is good for about 2 MOA with 34 grs. of AA5744. These are with the heavier military style brass. E