HaHa: 0
Duo lock in whatever size I find on sale. Never had one come open. Black ones for me but use silver ones too. Fish don't seem to care. Always leave split ring, trying for as much action as i can get. If I use any swivels on anything they're sampo ball bearing stainless.
As to hard to open and close, I sometimes have to use my hemostats to open them. Not so much because they are hard but the hands or cold or the snap been mis shaped by a catfish or snag. Generally they aren't too tough to open.