I used both and had no real problems with either. I used them for 15 years each so the user report could be added. I kept the '64 tight and clean and in good shape so it didn't fall apart. I was careful assembling and disassembling the '82 so the plastic and eyes didn't get destroyed. I was Infantry and have still the slim waist of the regular Infantry, so if you kept the webbing adjusted to you it worked fine. I was around still to be issued the tactical vest...
However...both types weren't soldier proof and equipment pretty much has to be. The combination I created with a '51 pattern belt and "H" harness, two M14mag pouches and US water bottles was almost spot on for the '82 pattern but was far tougher. It couldn't possibly fall apart. That was in about 1976 so we still had the FN and carrying mags in pockets was bulky and clumsy. I personally didn't like using the '51 ammo pouches much as they hung down and were bulky. They were mostly issued for the SMG C1 EIS.