To add, if OP was interested in measuring group sizes, he likely wouldn't be posting this thread and would instead be looking at a hyper-acccurized AR or Remington 700. I'm willing to bet that if you compared the average American conscript GI with a M14 to an Aussie or Kiwi with a L1A1 in Vietnam, the guns wouldn't be that much different in accuracy. To get the M14 platform into its current state took decades of development by CMP shooters - the guns weren't shooting 1MOA in 1963 except for the match guns.
To give any meaningful statement about which gun is more accurate, we should be comparing specific examples, not making vague generalities. Because none of us are comparing an actual FN FAL to an actual mil-spec, select-fire M14.