The games are created and set up to maximize the potential of the AR15. If you shoot something else you will be handicapped. Now, if they set it up to favor the 7.62x39 in a Kalashnikov platform my advice would be different.
I shot "he man" a couple times, it was a lot of fun, but those guys who drive the AR's are, many of them, just fantastic athletes with great skills to watch.
Much as I dislike the AR15, they are the gun to beat.