"some small argument being made (one that I'm not really convinced by, but here we are) that they weigh less, and thus improve the sound somewhat."
There may be another thread somewhere about this weight issue. Apologies for hijacking this thread. I briefly discussed weight in an email with Jake at The Bass Spa. We talked about the weight of the endpin and the weight of the tuners and that if they were both lighter the bass could sound better. I have a heavy Gallery Strings end pin on one of my instruments and factory-bass Tyrolean plate tuners.
The last time I was in Jon Peterson's shop (RIP) he had an old Sloan tuner on the bench. I picked it up and was surprised at how heavy it was. I just couldn't imagine the weight of 4 of them on a bass. The ebony shafts of hat peg tuners would certainly reduce a lot of the weight.
So....I'm thinking a carbon fiber end pin, Laborie style possibly, and hat peg tuners would lighten my instrument considerably. As to the sound? If I ever make these changes I'll post the results.
further complicating the issue is that many of the basses that have "hat pegs" are just decorative, with regular metal tuning shafts.