From what I gather, the M1 is a more accurate rifle and the 7.62x51 is a more accurate cartridge. To get the best of both get a M1 with a 7.62x51 barrel - that is if you're serious about paper punching.
I like the M1, I have two, one I've shot in matches and the other is like new. I'd like a M1A, but only the most accurate one I could find. I liked the M14, I'd really like to have the one I was issued. But M14's are crazy priced and I don't need nor desire the full auto function, though it would be a neat show and tell option.
Maybe I'll find a M1A that has my name on it, someday.
CMP has M1's for sale, now and then.
