the m4 is more accurate but has a smaller round, smaller round is faster though, ive shot an ak out here but I like my M4, I had an M249 which is a machine gun it also used 5.56 round, im a fan of the 5.56. Ill probably buy my own AR15 when I get out of the Army. Im gonna take pics of our crew serve weapons tonight and Ill post them tommorow, one shoots a .50 cal round and the other shoots 60 40mm grenades per minute.