Re: M1A or AR
Yes, M-14s will tend to be more reliable than ARs, especially under adverse conditions. One thing I have noticed is that when they do malfunction, they are easier to clear than an AR. They also unquestionably have better iron sights... great sight radius, and with nice 1 MOA clicks for both windage and elevation right at the rear sight.
However, ARs come more accurate out of the box. Most M1As I've shot are 1.5-2 MOA capable. Most .308 ARs are more like 1 MOA or under. It will take a bit of work to make your average M1A as accurate as your average AR comes out of the box. AR's are also easier to mount optics on.
When it comes to weight, it varies a lot based on how the rifle is equipped. I think when both rifles are equipped similarly, as far as barrel length and weight, they are about equal. A GI M-14 weighs just over 9 lbs. That's not very heavy. An Armalite AR-10 with the 20" chrome lined barrel weighs just about the same. Whereas a DPMS LR-308C with a HBAR 20" barrel weighs over 11 lbs, just because the barrel is fatter under the handguards. You can get a .308 AR carbine with a light profile barrel that will weigh less than a standard 22" barreled M1A, but you can also get shorter, ligher M1As like the Scout that will also weigh less. Most of those after-market stocks for the M-14 like the Sage, JAE, and Troy add significant weight though. The Vltor Modstock is the only one that actually weighs less than the GI stock.
When it comes to cost, I don't know that the AR has the advantage... they seem comparable for the quality you are getting. A Springfield Armory, Inc. M1A is basically a mid to upper quality rifle. You can get an AR cheaper if you go with a DPMS, Rock River, or Bushmaster, but AR guys will tell you that those manufacturers are on the lower end of the spectrum of AR manufacturers. You can also get an M-14 cheaper if you go with a Norinco or Polytech... I'd put their quality on par with DPMS. I put the quality of an Armalite about on par with Springfield, and they cost very close to the same.
For high-end M-14s, you are looking at 7.62 Firearms, Fulton Armory, Smith Enterprises, and LRB, which are 2000 bucks on up. For high-end .308 ARs, you are looking at Noveske, LaRue, LMT, KAC, POF, and LWRC, which are all over 2000, and on up over 4 grand.
Basically I see the M-14 as a great battle rifle, whereas I see the AR as a great range rifle or long range precision rifle. I have an M1A currently, but I am wanting to build a .308 AR on a MA-Ten receiver. I don't plan on getting rid of the M1A though... at least not until I sufficiently test the AR and find it to have acceptable reliability under field conditions. I am a big believer in always having at least one rifle that can take care of business under all conditions. Right now, my M1A is that rifle.