they're much smaller than a 9mm Glock.
Not really. They're the same basic size as the 26, just a tad thinner.
Even so, I can only understand the popularity of the G42 because of the assured basic level of popularity of essentially any Glock product with Glock fans. If any other company had designed the gun, I think most people would label it an utterly pointless creation.
They are an easy sell to anyone who likes Glocks. Its another "baby" Glock, and everything works the same.
I was fighting the urge to by one, and was waiting for the 9mm version to show up, until I gave in, and bought a 42. Now that I have them, I really dont see Glock going the single stack 9mm route with them, as they dont do anything better than the 26, and in a couple of ways, they are lacking, that being, caliber, capacity, and not being able to use the larger guns mags as a reload, or change of capacity.
Still, they do offer another option in your depth of carry, and its basically the same gun as the others.
Ive shot my 42's quite a bit now, and while like them, I see them like the 19, and Im still trying to figure out their point and place in the scheme of things. I still carry my 26's, and the 42's arent likely to replace them. Probably just become the 26's back up, if I need to ditch the 17.
I suppose if you like the .380's, its an option, and it would be one better than most. I have, and have owned a number of smaller to mid size .380 pistols over the years, and the 42 is one of the few that was soft shooting, came with decent, usable sights, and can shoot at a distance, like a larger, or full sized gun. The only other that came close, was the SIG P238. Unfortunately, my P238 was not at all reliable, something the 42 has been since round one.
Personally, Id recommend the 26 over the 42 if its going to be your only gun, but the 42 will do you better than most of the other .380's, if thats your thing.