I own a 226 and a 220 in the P series and I also own a 2340. Do I like Sigs? You bet, and I do think there is a difference in the alloy frame to the plastic. But is it better or worse? It depends on what you like. I admit I am a traditionalist so I like the feel of the alloy better. I also like the visual appearance of the P series. As for shooting, the 2340 and my 226 are equal. Yes, they do feel different, but the holes end up about the same place. I think the 2340's trigger is better than all of them. It is also more comfortable to shoot. I have small hands and the small version grip fits my hand very well. As for reliability, I can't say. None of them have EVER givne me a failure to feed or eject.
I also own a Glock 23 (gawd, I hope my wife doesn't read this) and sold my USP Compact in 40 S&W. The 2340 is much better than the Glock and somewhat better the HK. The HK was good shooting, but pins kept falling out whenever I cleaned it. But, keep in mind the 2340 is larger than any of them. I do not rate it as a concealable. If that is what you are looking for, go with the 229. Different guns, different missions. I know the 2340 has not been a good seller in the U.S., but I don't know why.