Continuing the discussion, here are some random musings:
1. 7.62 x 39 is (statistically) slightly less lethal than 5.56 but a good hit with either round will be VERY BAD for the intended target. Neither is a death ray; either will do the job. I've seen torso hits from both...I'm a believer. This applies to most military caliber centerfire rifle rounds.
2. Re: 5.56 vs. 5.45...roughly same-same...it's a wash.
3. AK iron sight accuracy ranges from barely OK to adequate (out to 300 meters); AR accuracy ranges from adequate to good (out to 300 meters). A good shooter can wring out significantly more long range accuracy from the AR, especially with A2 configuration.
4. AK has abysmal ergonomics (poorly located magazine release, short sight radius, poor rear sight eye relief, adequate but not great trigger pull/break, and the world's worst positioned selector/safety). This REALLY comes into play when you are in the company of other like-equipped friends and in contact with the other side. Immediate action drills, weapon safe/clear drills, transitions during CQB, vehicular drills, and Individual Movement Techniques (IMT) all suffer with the AK. The gun is either hot (safety off) or its not (safety on). Manipulating between the two requires way more time and motion than with the AR. If you don't think this is hugely important, you are dreaming.
5. The AK selector design is one which provides for a high probability of fratricide or Accidental Discharge (AD) once friendlies start operating in close and heated proximity to one another. You can either opt to carry with the safety off (AD waiting to happen and dangerous even for a point man) or with the safety applied (requiring 2-3 seconds to disengage). With no hope of reacting to a close-in threat (the other guy is already inside your decision loop), you lose. Your only option is to forget the AK and seek cover (if you make it there before being hit). Show me an AK-equipped squad in contact and I'll show you SOMEONE flagging their buddy with their muzzle (safety off / finger on trigger at some point). Think it won't happen? Think again...
5. The AK was designed to support a discredited infantry doctrine which had Soviet troops advancing (during final assault) on line w/ everyone firing short suppressive bursts at the objective (as they did with SMGs). The initial movement of the AK selector to full-auto is insane and of no value. We (US Army) no longer doctrinally teach full-auto rifle fire except for certain IADs where supressive fire is desireable. Our guys practice aimed fire at distance and controlled pairs up close. The hits with hollywood full-auto just don't happen reliably enough.
6. AK with a folding stock carries nicely in a vehicle (better even than a collapsible stock M4). On the other hand, firing the damn thing without the stock unfolded is almost useless beyond me-to-you range. Watch any of the amateur-hour clowns who routinely macho-pose for the cameras on the nightly news from the Middle East. They run from the safety of a corner or alley, spray a few rounds down the block, and come back grinning. Kind of like firing a pistol gripped shotgun...impressive for the cameras but ineffective.
7. Despite its shortcomings, the AK is effective, reliable, and easier/cheaper to manufacture than the AR. It's also cheaper for the US civilian shooter to buy. In the "baby-needs-new-shoes vs. daddy-needs-new-toys" equation, a $300 SAR-1 delivers more bang for the buck than a new Bushmaster. Is the AR the better rifle...yes. Snob appeal aside, will the SAR-1 get the job done (SHTF, plinking, range fun, home defense)...yes. Would I equip a modern army with the AK (even the modern Russian versions)...no.
8. Crosshair brought up good points. Know your chosen weapon. Know its advantages and its limitations. More importantly, know your personal abilities and seek to utilize advantage / minimize limitations (regardless of the rifle in your hands).
9. BTW, I LOVE my SAR-1.