I voted for the 43.
I jumped on the 43X/Shield mag bandwagon when the mags became available, and have carried it OWB at 4:00 quite a bit. It doesn't shoot any better than the 43 for me, it just holds a lot more; but I can't pocket carry it.
Last year I acquired a G26 in a package deal, after avoiding them for years because they "feel terrible in my hand". It turns out that I shoot the the G26 better than any other Glock, including the full-sized ones (maybe better than any other pistol, period, except for slow-fire, bullseye type stuff), and it carries OWB at least as well as the 43X, actually concealing better with the flush-fit mag. It shoots the same for me with or without a pinky rest/extended mag. Suddenly, it feels really good in my hand.
So, the 43X occupies an odd slot in between the 43 and the 26. Instead of being a Goldilocks, it's like a dual-sport bike: doesn't really suck at anything, but isn't great at anything, either. The only real advantage is the increased grip length makes for easier mag changes. I imagine it would carry IWB better than the 26 because it's thinner, but my craft beer issues make that uncomfortable.
If I had to choose only one carry gun, it would be the standard 43. It shoots well, disappears OWB, and I can pocket carry it.