I'd pick the M1A from the three listed if I needed a foxhole companion. I know little about an AR 10 but am not enamored with the AR design overall. The 7.62X39 makes more sense as an intermediate cartridge than the .223 in my view but the rifles for which it is chambered don't have the accuracy reputation and it doesn't offer the long range punch of the bigger .30.
My plain-jain, unfooled-with M1A offers really wonderful accuracy from the bench rest or the firing line of a high power shoot. It has always given dependable service over extended shooting sessions. It also has proved to be surprisingly reliable with efforts to develop minimal "powder-puff" loads that are crazy light, giving reliable function even while sounding like a pump shotgun being cycled. It is a good dependable rifle.
