The buffers feel different, I honestly can't tell the difference from a semi or m16 style BCG. For reference, the m16 is lighter then the semi, not the other way around as you posted.
The good news is buffers are cheap. Heavier buffers are more of a factor of reliability, as more mass will cause more of a recoil impulse. "Milspec" weapons used for bench shooting are less comfortable then benchspec rifles used for bench shooting. Benchspec rifles used for milspec training will fail often. Use the right tool for the job at hand.