I tried some bespoke shirts with separate collars.
The only benefit that I can see is being able to switch collar styles, such as self-collar, soft, startched, cutaway, etc. Otherwise, unless you wear a highly startched white collar, a soft separate collar will look no different than a regular attached collar.
My problems with the shirts:
1. On one shirt the collar and the shirt ban did not synch together. One was too big for the other. And this was from one of NY's...