threadless-
- advantages
- stiffer due to wider diameter materials(i think)
- easier to swap stems
- disadvantages
- not as elegant
- more difficult to adjust height




threaded quill-
- advantages
- easy to adjust height
- elegant
- disadvantages
- difficult to swap stems
- incredibly limited stem angle selection
- flexible


I have threadless quill adapters on 2 bikes for utility over beauty. If quill stems came in a 7degree rise, I would own 2 of them. Unfortunately, almost all were/are limited to -17deg. The rare one that isnt, the Nitto dynamic II, is 65mm from the min insert to the top and seems to only be 110mm or longer. More legit quality angle options back in the day woulda been nice for the secondary market now.