Almost everybody on here has fallen prey to the myth that M16/AR-15s jam.
If the M16 series is treated correctly, then it will never, ever jam. Unless your in a very poor enviroment (Iraq, for example), and don't clean your gun as often as you should (about once/twice a week), then your gun WILL jam.
Here is my comprehensive review of the Guns IN REAL LIFE.
Caliber:
M16: 5.56mm
A smaller round, and is shaped similar to a needle. This gives it the advantage of being able to fly further, faster, and with more accuracy. However, being a smaller round, it has less propellant to project it, meaning it has less stopping power. Its pretty common to hit a guy a few times before he stays down. (From my Uncle, Marine)
AK-47: 7.62mm
A larger round, meaning it has more stopping power. Its nose is rounded more, so its a slower, less accurate bullet. Packs more of a puch, if you can hit the target. But if it hits you, you aint getting up.
Mechanisms:
M16:
Relatively complex. A lot of parts, which means thats a lot of parts that can get broken. However, if properly maintained, then you shouldn't experience any problems. If anything, most cases of 'Jams' in Iraq/Afghanistan have actually resulted from the barrel partially melting, then hardening, and interrupting the ejection of brass.
AK-47:
A simple design, though considering its WWII tech, what do you expect? Works to the AK's advantage, though. Cleanup is a breeze. Litteraly soaking it in water for a few minutes is all you really have to do, besides oiling the parts occasionally. You can put the gun through hell, and it'll come back in one peace.
Accuracy/Recoil:
M16:
The gun easily surpasses the AK in all aspects. It fires a round that slices in the air, and coupled with the fact that the M16 is capable of Single Shot/3 Round Burst/Full Auto, its versatile as well. And because nothing scares the crap out of you better than Amerians screaming 'BOOM! HEADSHOT!'
AK-47:
Though it looses out to the M16, it still is respectable. The round it fires is larger, though more sluggish, and at longer ranges has the tendency to 'wobble' in the air. The gun basically sacrifices accuracy for power.
Fear Factor:
M16:
About average. As I said before, the gun is really accurate. And theres something freaky about all your friends' heads kersploding at 400 yards. The gun doesn't look that intimidating, and it sounds almost friendly, if it weren't for the hot lead coming out the business end.
AK47:
This gun is scary. It looks scary, it sounds scary, and most people admire it from the ground with a hole in their chest. A considerable amount of this fear, though, comes from the Coldwar: Hordes of Commies with this iconic gun rampaging across Europe.
***Most of this information comes from several sources:
-Family: Several members of my family have been in the armed forces and have used the M16, or own the AR series or the AK series.
-Personal: I've shot both guns, and researched both, and have manuals on how to build the guns, so if that doesn't make me somewhat qualified, well...
-Books, etc: TV shows on the Military Channel, and books by soilders who have used the guns. Pretty good reading/watching.