Blood of Prokopius posts on the D6 weapon damage thing, making this point:
Having d6 damage has given my players the freedom to use weapons that they wouldn’t otherwise use. The main party fighter uses a spiked club, which he is very attached to. Once variable weapon damage is introduced (especially as written in AD&D) fighters almost always go for swords — why settle for club at d4 damage when the long sword does d8? In practice, the universal d6 damage has resulted in creative play — since everything does d6 damage, advantage in combat comes from tactical choices outside of weapon choice. As a gamer, I’ve really enjoyed this creativity — aesthetics.
Often, particularly with NPCs, I assign “other” weapons as a sort of characterization. This is really cool in my mind, but then the NPC finds itself over-matched in combat because the PCs all have optimum (dice-wise) weapons. Which is a bummer.
Again, I really like the idea of all-D6 weapon damage, but it doesn’t work so well when the system uses hit dice greater than D6.