I do not like the new RCBS because the setscrew damages the thread. The old style split ring RCBS used to make was the best. Hornady still makes these types.
Lees Orings su?k The O-ring can not be set in a memory position (Set & Forget) seating & belling dies and must be readjusted after each use it. Not criticizing Lee dies as I own a few. I have replaced all Lee Oring lock nuts on all dies except the sizing dies.