Yesterday I told S&W I want my Shield back. I'm not taking the deal. That's the one where they cut up and destroy my cracked frame and sell me a new pistol as part of their "replacement" program. I'll take the cracked, non-functional one back. That's the one they wouldn't warranty.
A hundred fifty bucks difference in cost (more like a hundred, between cost of the Shield and the G43) is about ten boxes of ammunition for a 9mm; 500 rounds. That's two and a half times more than the Shield lasted, before the frame cracked. Another way of looking it that might be the cost per shot, and that made the Shield exceptionally expensive, to say nothing of untrustworthy, unreliable, with an unbelievably bad warranty.
I haven't had my G43 for long; it was a gift. They don't sit on the shelves around here for long, whereas Shields are in every store and can be had without any problem. I doubt I'll have any need to try the warranty, but I have no doubt that should I need the warranty, I won't have any difficulty from Glock. Based on numerous calls and emails over the last few months, I can't say the same for S&W.
Stock, both the G43 and the Shield have poor triggers. Both are light, both are compact. The shield is comfortable in the waistband, and so is the G43. Given the choice between carrying something bigger and more capable, I'd chose the latter; I wouldn't ditch a favorite firearm in favor of the small single stack in 9mm, save for size. Light clothing, tuckable situations, ankle carry; those are areas where a light single stack like the G43 shines. It wouldn't be my first choice if I were faced with engaging a shooter at a recruiting station, for example, or two shooters at a cartoon convention. I'd rather have something more capable, with more capacity, but that's just me. Then again, I'd rather have a rifle.
Carrying a rifle isn't always practical, so we compromise, and the compromise continues to whittle down what we can carry based on the situation, location, clothing, etc. Under circumstances where nothing else is possible, the G43 will prove a reliable option. It's low capacity, has a poor trigger, has a short sight radius, has a very small grip, and comes only in 9mm (for those that care), but it's what Kahr and most other small pistols should have been. The trigger can be improved, better sights can be had, and there are always options with the grip. One can always carry additional magazines. It's not the pistol one wants in a protracted gunfight. It's got equal the capacity of a revolver (for those of us who still feel comfortable with a revolver), it feeds most everything put in it, and it comes on the heels of a long line of very successful pistols and is made by a manufacturer with a very solid history of taking care of its products and customers.
Get both. Shoot both. See for yourself what works best for you. If you do have a problem with the Smith, don't count on S&W to help you or take care of your Shield. Hopefully you'll have no issues with either one. Given a choice between the two, my recommendation would be to get the Glock.