The 43 just fits some peoples hands better than a 19. My wife is the prime example of that.
Exactly , the release of the Glock 42 and later the G43 was the first time I was ever enthused abut the possibility of owning a Glock. Up until that point there was not a single Glock model I was interested in. The double stack Glocks were the most non-ergonomic grips for my hand across the entire line - none felt good. The G43 fit my hand very well but I did end up with a Smith Shield. But did pick up a G42 not long ago which is probably the best fit to my hand of any semi-auto defense gun.
And I like a thinner gun for concealment compared to a "fat" gun.
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The single stack 42 and 43 compared to a 26.