I think there are a few big reasons for AK variants being more widely used than M-16 derivatives: - 7.62x39 was made popular by the SKS and it made sense for t

I think there are a few big reasons for AK variants being more widely used than M-16 derivatives: - 7.62x39 was made popular by the SKS and it made sense for the AK to be compatible. With that as the dominant round in many areas it makes sense to use a compatible rifle. - The AK variants with stamped receivers are very inexpensive to manufacture. - The gas piston system is more reliable for rifles that are not cleaned regularly. The M-16 and derivatives are common within the US's sphere of influence though.