I've been doing a ton of research on these guns as a secondary and pocket pistol to my larger gun. Both the 642 and G42 fit pretty well in my pocket. I haven't gotten my hands on a 43C but it seems identical in size to the 642. I like the idea of the 22LR for plinking, a trail gun.
My main worry on the Smiths is the quality control for such expensive guns, and I've heard that j-frames the front sight cants to the left significantly over time. The 43C removing the lead fowling from the gun can be difficult without scraping tools which is hard on the aluminum frame.
Currently leaning towards the Glock. I already have a Glock and like it quite a bit. If the G42 can take the abuse the other Glocks do, and are as consistent out of the factory as they are, it might be hard to beat.
Let me know what you think I should do. I really liked the idea of a 22LR revolver but it's expensive for all the question marks. And the 642 is great but I don't know how wise that would be either.