Hard to explain without pics to compare but the Shield is a lot beefier built. It's a gun that I'd shoot just as much as it's big brothers and not worry about breaking things, just replace the recoil spring a little more often. It appears to have the same type locking blocks as the full size. I can't say that about the G43 in comparing it to it's big brothers. Field stripped the G43 looks identical to the G42. Would you really want to rechamber a G42 (.380) to 9mm and shoot 5k rounds? It appears that that is exactly what Glock has done. The G43's slide is very slightly wider and I suspect it's very slightly heavier but there's really not enough size difference to even discuss. I could be wrong about the longevity, time will tell.
Then there's the feature set. The Shield has better sights out of the box, the sights are made of steel, the trigger is light years better (at least on the one that I did a side by side with) and it holds more rounds. Cost is about $100 less than the Glock. It's a no-brainer for me.
Disclaimer: I don't own nor have I owned a G43, but I did compare the two, even field stripping them side by side. I did pick the G42 for my wife and it is a fun little gun to shoot.
