Pencil vs A2, personally I really like pencil barrels, but it all depends on what you plan to do. Me personally I shoot offhand, and usually just a 20rd mag or two at a time. I don't expect benchrest accuracy, I never get the rifle very hot, and I feel the difference in weight even on a 16" gun, so pencil barrels are a natural fit. If your idea of a range day is shooting 100 rounds pretty quickly from a bench, nitride/A2 may very well be the better fit. Speaking of accuracy, it's like another poster mentioned. By the time you start shooting 2-3 MOA bulk ammo with a 2 MOA dot sight or irons and pulling an 8 lb mil-spec trigger, any intrinsic difference between SS and nitride is going to be unnoticeable. Barrel wear, I've never shot out an AR so I can't say for sure, but I'd be surprised if either one crapped out before 5000 rounds.