the M4s spray pattern is more consistent than AUG without scope for like bullets 2-8, same as with Krieg, Krieg and AUG have very low inaccuracy, but they have 2x as much vertical spread on the recoil pattern as AK and M4 have. with the M4A4 i feel like this is almost completely negated by the quick right to left motion you need to make after pulling down for the first 5 bullets, so its really only about bullet 2-5 for me.
in other words with AUG you should only spray without scope short range, spray only at mid range with scope, and only tap with scope at long range. with M4 you can spray at short range, spray at mid range and burst 3-5 bullets at long range or say fuck it and spray at all range every time
M4 is also better for ppl with shit aim because its less accurate so even if you aim at the wrong pixel you still have a chance to hit.