I don't favor a thumb break on any holster, short of horseback use. For LEO's it makes some sense as they may have to wrestle with a law breaker. A good fitting holster will not allow the piece to fall out, and unless you're an LEO or participating in one of the combat pistol 'games' which sometimes require somersaults etc. you'll be well served by a strapless design.
The old Tom Threepersons open top is quite popular, works well from the tried and true FBI 4 o'clock position and is about as fast as is possible for presentation. A Yaqui slide is also good, but be sure you get one that tightly fits your piece. I like and use them both for CCW.
Best Regards, Rod