I'll be brutally honest, the reason an AR or M-16 doesn't jam has to do more with the way the weapon loads than the quality of the magazines. USGI magazines are junk really, but you'll hardly ever see an AR or M16 fail to load.
With the tolerances in the machining and the way the gun loads it's kind of a miracle they are as accurate as they are.... it baffles me for sure and I'm a mechanical engineer used to considering part tolerances and tolerance stacks etc. The AR / M-16 is a marvel of a firearm.
From what I can tell, I prefer the new composite magazines over the USGI ones any and everyday. They feed the bullet much flatter.
Now if you want to see a weapon that is magazine sensitive I recommend you get a Beretta M9 or model 92. I've seen the stovepipe bullets all day long because of a slightly used magazine.
At $22 I'll keep getting PMAGs and if I want to be cheap Tapco magazines.