I shot a few rounds through a G43 when they were brand new. For a compact 9mm, it is nice. the problem I have with it is that it's single-stack, and thus the magazines won't work with any other glock pistols. (I know it has to be single stack to be slim.)
To me, that is a big plus for the 26. I can own a 26 and a 19, and only buy G19 magazines. That said, i have never tried to carry a G26.
I'm getting really picky when I 'complain' about the 43, but to me it eliminates one of the best features of the other glock pistols. I'll say it again so people don't try to call me out on something I'm freely acknowledging: I am working to find a fault with the G43, and 'complaining' about something that wouldn't even be a possibility with most other 9mm pistols. It's me being hyper-analytical, not a legitimate criticism of the gun.