AR, all day, every day. I think the difference in stopping power is overrated, much like how a 9mm wouldn't kill a mean kitten, whereas everyone knows that even a single near miss from a .45 will result in potentially fatal trauma. Other than that, the only thing the AK has got going for it is reliability, and since I'm not an illiterate goat herder who uses lard for gun oil, I don't see much of an advantage.