M4 VS AK47

This is honestly personal preference.
Yeah the AK may have better damage, but it's also got ~bad~ recoil, if you can control it then it's an all around good choice.
The M4(A1-S) may have a bit lower damage, but it also don't have as bad of recoil.
The firerates are different, I believe the M4(A1-S) have higher firerates than the AK.
If you can master the AK, it is a better choice, but it depends on the situation, and is all really personal preference.