From what I gather, the only question of "absolute reliability" concerns folks who carry and use their rifles under combat conditions. For hunting or target shooting either is plenty reliable.
I went through a period where I seriously considered a Smith & Wesson MP-10 or a Springfield Armory M1A Squad Scout.
Both are relatively light at 7.7 lbs. for the Smith and 7.8 lbs. ( actually weighed ) for the synthetic stocked M1A Squad Scout.
Both are reported to be comparably accurate, on the order of 1.5 or better MOA for five rounds with ammo they like.
The biggest drawback for the M1A is it's is stocked for iron sights. Mounting a scope on a good tough mount is both expensive and places the scope very high over the rifle, or one can use a scout scope.
The M&P will take anything in a scope, but it sits very high on the rifle, which is bad for a guy that tends to cant his rifle when shooting.... Their triggers suck as well.
To me the M1A handles/feels better. So I gambled and bought one even with my concerns for it requiring a scout scope.
It has worked out very well. The Leupold VX2, 1.5-4X Scout Scope is alot sharper and more useful than I ever thought it would be. Probably due to the 6-6.9 inch eye relief vs. the standard ER of 9-14 inches that most classic scout scopes have.
It shoots regularly under 1.5 MOA with several of my handloads. And the trigger is so good, it has the honor of being the only rifle I've bought in over 25 yrs. that didn't need a trigger job. Very consistant and very crisp.
So, I'm happy with my choice. E
