The versions of AK, other than the AKS versions are mostly the same weapon with superficial changes.
Caliber changed. AK-47 and AKM used 7,62x39mm, while AK-74 familiy - 5,45x39mm. Those are two VERY different types of ammunition. In Russian forums there is mirror of our discussion, but in other way: which type of AK better, 7,62 or 5,45mm? Again, both sides have their arguments: 5,45mm gives considerable increase of accuracy (~1,6 times better over 7,62mm chambered AKM) and allow soldier to carry more ammo with, while 7,62mm round is more stable and has more of penetration power (it's quite important in urban and forest environments).
But I think what we're talking about here is the modern weapons, not what was used in Vietnam.
As we can read above, Mr.
bulldog disagree with this statement
Besides, despite of AK-74 being standard infantry weapon of Russian Army, some unit or soldiers continue to use `old` 7,62mm chambered AK's (usually AKM/AKMS, I have not see any evidence that AK-47 is still in use in Russian Army).
The current AR-15/M-16 family vs the current AK family.
And like I said, under most conditions I would rather have a weapon I can trust to hit the target with than something that sacrifices accuracy because I know I can clean my weapon enough to keep it ticking.
As for your claim that the AK is better suited for shooting things that move... that's quite a claim for a weapon that has trouble hitting something staying still.
At first, best barrels of AK-74 gives out an accuracy of 1 MOA in 300m distance; reference - Sniper Notepad:
http://www.hpbt.org/articles/cezar.htm
At second, using semi mode AK-74 is accurate enough to hit all the relevant targets within 300m. For distances above 300m - fire mostly for suppression and, if accurate hit is needed, it is what SVD is for.
At third, most of fire from small arms is fired not for sniper-style direct hit, but for suppression. And there is no need for accuracy `to hit a bull's eye from half mile` for standard rifleman weapon.
At fourth, and what if situation would be such, where scheduled cleaning of weapon is not impossible? For example, your unit is surrounded in swamp or in desert during sand storm (and there is no to place parts of dissembled rifle where they wouldn't get moisture or sand particles inside).
It doesn't mean, that M-16 family is not suitable for anything. M-16 is good weapon for professional, well equipped and relatively comfortable dislocated (i.e., soldiers have opportunity to clean their rifles at least inside armored vehicles, especially in aggressive (sandstorms, often rainfalls) environment) units.
So, both of these assault rifles, M-16 as well as AK are either good for riflemen units. For special forces, especially in urban environment, I think M-16 family will be much better, while AK family will be best weapon for mass conscripted army.