i use an AK as my primary go-to rifle, however, with the caliber choices available to me (7.62x39, 5.45x39, and 5.56x45) i went with the 5.56, ballistics on the 7.62 are not anything im going to be fond of, it hits hard inside 200 yards, sure, but outside of that range the 5.56 carries more energy and will shoot much flatter throughout its entire trajectory, and inside 200 yards the 5.56 is carrying all the energy it needs.. its an all around much better caliber
the russians recognized this and they pretty much abandoned the 7.62x39 after only 27 years in service, switching to the AK-74 and 5.45x39 in 1974, theyve been using this caliber for 41 years now and will likely continue to do so in the foreseeable future
so as badass as people like to think the 7.62x39 is because the ruskies used it, they fail to realize they also abandoned it as well and went in a different direction shortly after, so the russian military didnt think it was as good
i think the AK is better than the AR/M4/M16, but i think the 5.56x45/223 is better than the 7.62x39