My 5906 has a VASTLY superior DA trigger compared to my P226. But, the P-226 has a better SA trigger, IMHO. I also get a little better accuracy from the P-226. YMMV.
I greatly prefer the 3 dot sights on the 5906, and how the weight helps soak up recoil, compared to the P-226. My 5906 'controlled rapid fire' groups are significantly better than I can do with any other semiauto.
Both pistols are very much very high end semiautomatics in terms of engineering, workmanship, function, and reliability.
The P-226, even used, will cost more, however. Like HK's, Sigs have ALWAYS been expensive semiautomatics, and they seem to be much more sought after in the used market, compared to S&W semiautos.
I still know a couple of gun show dealers who will either refuse to take 2nd and 3rd gen. S&W semiautos in trade, or offer a pretty low ball price.
Since the invasion of polymer pistols, all metal, especially all steel, full sized semiautos have fallen out of favor; with the great unwashed masses, anyways.