A few comments:
It is correct that the AK series guns are rugged and reliable even with little or no maintenance. They were designed for a huge conscript army of many nationalities (and languages) and variable educational standards. This explains the Soviet preference for foolproof kit.
The M16 is reasonably reliable by the standards of Western military rifles, but it does need more looking after, especially in the dusty conditions you get in the Middle East, where frequent cleaning is necessary. The problems with propellant causing jams were solved about 35 years ago. The upside of the M16 is that it is much more of a precision instrument and can shoot very accurately. The AK's heavy bolt group and deliberately loose tolerances, designed to aid reliable functioning in all conditions, result in a much less accurate gun (although the accuracy is sufficient for most military purposes).
The relative effectiveness of the ammunition concerned - the M16's 5.56x45, and AK's 7.62x39 and the AK-74's 5.45x39 - is a controversial issue and you will find little agreement over it. What is undeniable is that the small-calibre high-velocity (SCHV) 5.56mm and 5.45mm rounds are lighter than the 7.62's so the soldier can carry more ammo. They also develop less recoil which helps accuracy, especially in burst fire. And they have a flatter trajectory which also helps accuracy and gives them a longer practical range.
Where the SCHV rounds fall down is in barrier penetration (NB - this is different from penetrating hard armour, at which the current 5.56mm ammo is actually quite good). But at blowing through walls etc, the bigger bullets are better. A bigger bullet also provides more consistent performance when it hits somebody. It isn't necessarily better, as the SCHV bullets can be devastatingly effective if they work as planned, but that doesn't always happen.
The US forces have kept the older 7.62x51 M14 rifles in use (and pulled many of them out of storage and refurbished them for use in the Middle East) because of their greater barrier penetration and more reliable performance. But the 7.62x51 NATO ammunition is much more powerful than the Russian 7.62x39. US Special Forces have recently adopted a new rifle, the FN SCAR, in two calibres - both 5.56x45 and 7.62x51.
The Chinese have adopted a new 5.8x42 cartridge, which is probably the best of the SCHV rounds.
If you're interested in this subject, you might like
THIS article on my website, concerning the development of assault rifles and their ammunition.