Over the years I’ve used Schaller style or Dunlop and never had an issue with any of them (a drop of locktite on the nut on the Schallers).
Then… I had a Fender branded Schaller knock off fail on me Tuesday at a rehearsal. I looked down and the ball you pull to open it fell off. On that version it is impossible to screw back on while the strap is attached and very difficult to get off. From what I see online, that is its most common/only failure and the difficulty in getting it off the bass is a serious frustration. My son-in-law is a mechanical genius and was able to get it off in less than 5 minutes. In doing so boogered up the threads on the pin and offered to fix that but I decided to go with a new strap lock instead.
Searching it seems there are basically 4 different designs used - Schaller, Dunlop, Loxx, Ernie Ball plus the old fashioned washer type. Reading through posts and reviews, each type has true believers that love them and detractors who had one or more fail and so hate them. Each type has had failures, some due to user error and depending on the type, more due to design or production flaws. Son-in-law felt the Dunlop is the best design from an industrial point of view and the one he would choose. It also seems to have the fewest design/production failures from what I could see.
Here’s the rub… when one of the Dunlops, Loxx, or Ernie Ball failed, if the player wasn’t paying attention, the bass or guitar ended up on the floor. When the Schaller fails, you end up with difficult removing it. The instrument does not drop.
I ordered a new Schaller S model.