[squidly]

Just speaking from my own experience, I'll take the M14 over the M16, and the .45 over the 9mm. The only advantage I found in the 16 is that it's easier to carry. I always wondered why the U.S. military didn't put the M14 mechanism into an M16 style body. In every respect besides weight/weildiness, I found the 14 to be superior.
Likewise, I have never been able to see a decent reason for the switch to the 9mm. Not one.

[Shooter 2.5]

I always wondered why the U.S. military didn't put the M14 mechanism into an M16 style body.

You either decribed a .308 AR-10 or a .223 Mini-14.

Before anyone starts, the Mini-14 has the gas system of a M-1 Carbine and is notoriously inaccurate after the barrel heats up. After two years of experimenting with a Mini, the fault lies in the horribly manufactured barrels. It's even possible to bypass the gas system and the results are the same. It's an overpriced plinker.