Matter of taste and personal preferences. A big deal for some, minor for others, still others don't notice or care.
I like high reliability and small size, which (at a given price) the reverse clickys seem to be a bit better at (just an impression, no hard data).
With the advent of the multi-mode blink controlled lights (Fenix XXD-CEs, et al), I think I might like the reverse clickies more because it makes it easier for you to change modes in mid use instead of just at the initial turn on. But, then, that's only me.
If I WERE going to use a light with a handgun at night, I would certainly want a momentary on. I also would NOT want a tail standing light where the button is recessed - I'd want it protruding prominently to more comfortably control the momentary switch.