When I was on active duty, I prefered to carry the AK-47 (Romanian folding stock version) to the M16A2 or M4.
I found that the folding stock on the AK was safer and easier to handle during Fastrope and airborne ops. If you fastrope with an M16, there was a tendency to be butt-stoked by the weapon when you landed.
I found that the 5.56 round would be deflected in light foliage or moderate winds, while the 7.62 would not be affected as much. The 7.62 round is also easier to apply "Kentucky Windage" to since the splash of the round is easier to observe at medium-long ranges.
As far as the M4 is concerned, I hated it. Yes, it was a small package that was eay to handle, but that came at the expense of accuracy. We were issued the ACOG sight and that was a real boondoggle. Zero at 25 meters, confirm at 100 meters, and reconfirm at 250-300 meters only to find that the point of impact had changed at the greater ranges. I preferred my civilian AimPoint sight to the ACOG. The troops today have so many gimmicks attached to their M4's that it negates the weight saving benefits.
All in all, I preferred the AK series for the close in, heavy underbrush area's or CQB. The M16 was good for longer ranges found in desert area's. Both weapons are good when used within design parameters, or they wouldn't be as prolific as they are.
Opinions are hard to argue. Facts are a different story.
Let me make this real simple. Outside the realm of some feeling some might have, an M16 will outperform an AK hands down in near all measurable evaluative tests. I can measure the weight of both weapons. I can measure their length. I can bench-rest them and fire them, seeing which one shoots tighter. I can measure recoil. I can measure which weapon punches through more steel at 100 and 200 meters (Believe it or not, the M16 wins out there as well). I can measure a lot of things, but I cant measure what you feel.
The M16 is conceptually a more modern weapon than the AK47. The M16 is made using much more expensive manufacturing techniques and materials to make the weapon more durable, lighter, and corrosion resistant. The M16 is the Cadillac, while the AK is a Saturn. Some people simply dont know what they have and they really love their Saturn.
There are three reasons why someone would carry an AK for a *practical* purpose (Opposed to wanting to be a cool guy):
The dudes youre with all carry them and you want to share the same ammo, parts etc. Imagine youre working with a bunch of locals and they all carry AKs (Compatibility).
You want a weapon that sounds like that of the threat and fires green tracers. You can use the enemys weapon to confuse him or to blend in better and not stand out as much which ties into point one. (Confusing the enemy and blending in)
You want a weapon so you can do something very bad and illegal, i.e. a drop gun. Not your ammo, not your gun, not the ballistics of a 556 = I didnt shoot him in the head. (You intend to commit a crime)
From a functional performance aspect, you do not carry an AK. It is an inferior weapon. You dont IMT with an AK that has a folding stock, but you can with an sliding stock on an M4. Your AKs receiver is more easily damaged physically because the thin stamped sheet metal bends. The gas tube is more easily damaged as well. Finally, the weapon is actually more susceptible to rust. If you want a good AK, youd actually buy one made by a Houston Texas based firm because they use a thicker gauge sheet metal when stamping it. The AK was designed as a cheap mass producible weapon based on technology and concepts many years past.
For the Iraqis an M16 would be an upgrade over their current AKs, some of which are brand new.