I'm late to the conversation, but had been pondering the possible need for more rounds due to world situations than my trusty Model 37 affords. I finally "pulled the trigger" yesterday, and the Glock 43 was surely in the running.
In the end, I went with the S&W M&P 9mm Shield. Better sights, one extra round over the G43 with the Shield's concealment magazine (7 vs 6) and eight with the provided longer Shield magazine. Also, the grip angle provides me the "natural" point of aim I've come to expect with my other handguns.
The trigger didn't have the takeup mush of the Glock, with just a hint of additional takeup, though the pull was a little stiffer than the G43.
Time will tell . . . but then again, that 37 is my "always" (always on me) firearm, and I suspect it will still be my pocket gun to go with the additional firepower of the Shield.
Ironically, my wife also upped her firepower yesterday too when I got her to go with me. Her Model 37 3" couldn't travel on her all the time, of course. I thought she might go with the Glock 42 or 43.
Wrong! She went with the Ruger LCP in .380. THAT little pistol can be with her at just about all times, and that's the important thing!