I have a Glock 43 and like it. One major reason, though, is commonality of platform, which may not be an issue for the OP. The other reason is that I like to have at least one pocket 9mm in the stable. Although not ideal, the Glock 43 can be used in a pocket of my jeans or for the few times a year when I have to wear business casual type clothes. My only experience with the Shield was hefting it and realizing the Glock was better in the pocket. I also think the Ruger LC9S Pro would be better in the pocket than the S&W.
If pocket carry is not a consideration, I think the Shield would be a very viable carry gun, based on reports of those who have them. I would get the one without the thumb safety.
My early model Glock 43 had some teething pains for the first 150 rounds. It then ran about another 2500 without an issue, then started giving me some malfunctions that, tentatively, have been resolved by a new recoil spring assembly. Note that Glock is now on a second iteration of magazine. I have read, but cannot confirm, that Glock has changed connectors to lower the trigger pull weight to that of larger Glocks. That can be good or bad depending on perspective and proposed use. Don’t buy a Glock 43 before testing the trigger to see if you like it.
MOGC is correct about the Glock plastic sights being throwaways.
