For my own personal ownership, the A2 is no more valuable than the A1 so I bought an A1 (at the lower pricing). It's my understanding that the A2 reinforcements were made because military personnel were breaking the lowers by using bayonet equipped M16 rifles to pry open crates and occasionally leaving the M16s places where they were run over by tanks, trucks, etc. I have not and don't have any plans to ever pry open crates with my M16, though I do have a bayonet in a box somewhere; and I don't leave it lying around (not even getting shot much in the last several years).
MHO, YMMV, etc.