I use 3 degree. Any more taper seems excessive for the task, and 5 degrees only ever seem to be available in black, white, and occasionally dark brown... but the boxwood pins from LMI are my favorite, and they have lots of other colors as well in 3 degree slotted.
That said, 5 degrees do seem to be available unslotted more often, which is a good thing. You can always just turn slotted ones around, but I'd have to fill the slot with something or otherwise mark it, because an unsuspecting person could end up flipping them to the obvious slot-in-use orientation, which combined with a slotted bridge plate would only accelerate the damage compared to slotted pins with unslotted plate.
Does anyone know if Gurian (the source of LMI's pins, I believe) will do unslotted 3 degree pins? Maybe I should become a pin supplier, ordering batches of whatever colors I want and selling off the excess
Or maybe I should just get a mini-lathe and make them myself. I'd love to be able to use domestic woods like persimmon, mulberry, pecan, maple, desert ironwood... and rarely available exotics like pink ivory, ziricote, purpleheart, pernambuco, the many shades of Honduran rosewood, anything with some sapwood on the pin, and of course unslotted boxwood.