To each his/her own, but...
When I was working (32 years in LE), I obviously preferred extra retention as you could end in a fight for life at any given time. I switched platforms depending on what I was doing and where I was doing it. Personally, I never had a problem switching from a thumb break to an open top, I guess some are fine like that and others need to stay with one practice to be proficient. If I had to choose one or the other I would always opt for the extra level of defense and security. I've always been an advocate of thumb breaks as with sufficient practice and training, efficiency isn't a problem. Speed is needed but not nearly as much as situational awareness; it's rare when one needs to play quick draw McGraw vs having a sense something is off or of concern. Put together and weigh the two...having to draw in a split second PLUS the odds that you'll screw that draw up due to the TB - combined, the odds are most likely extraordinarily low. Then, weigh the odds of losing or dropping a gun because of a fight, car wreck, running, or any other daily function. Sure, there's great retention in today's open tops but keeping that gun under control and on your side is of the utmost importance.
Open carry is a whole other subject.