Which is better an AR 15 or a M4?

they are bothe very similar but i would have to say the m4 because of higher power and it is used by the military not like the ar-15 which is mostly used by law enforcement. It depends on the m4 though because there is a very wide variation of models of the m4 unlike the ar-15 which is one basic model... there isn't much difference between the m4 carbine and the ar-15