Well lets start with familiarity of the weapon and the skills of the operator, then we can go into the inherent accuracy or inaccuracy of the weapon.
To start with on the quality side, the AK is behind the game as it is not subject to the same QC levels that the milspec AR is subjected to. Now if he [you] were to throw up a bottom feeder AR for a side by side, where production was more important than quality, then we might see some more accurate results.
No argument, the Russians have built a true to life K.I.S.S. weapon that requires 0 maintenance and in the event of a failure, it will not be picky at all about taking parts form an organ donor.
Admittingly I know little to nothing about ARs, but 10 fold more than I knew last month. Tight tolerances means picky, and sensitive. That is one thing the AK is not.