Can't go wrong w.any of those three, but 19 and 34 are IDEAL complements to one another imo. You're covered from ccw to range/game fun, same configuration, same operation, mag and ammo compatability. And unless one is looking to "collect the whole set" lol, I always recommend skipping a model for reruns in the same caliber (ie 26 and 17 makes more sense to me than say 19 and 26 or 19 and 17 and, same w/19 and 34, "covers more ground" than 17 and 34 or 19 and 17). But I take a conservative approach to what guns I keep. Always trying to do the most with least. Nothing wrong w/collecting the whole set, or broadening horizon to different platforms.
Because ironically, despite my vote, if I were to do it over again, I'd have actually gone 17 over my 34, because I will not be buying a 19 (for MY ccw, anything not .4x nna). And have no complaints w/my 34- EXCEPT that I'd rather have it just come w/the stock plastic sights instead of the cheap adjustables, since you'll likely be replacing those anyways (and justsomething to think about, the sig will come w/quality sights out of the box). Would have made it cost less. If it were a choose one situation, 34 easy. But you have to consider whether extra sight radius (which the jump from 17 to 34 in sr costs money, while jump from every other model in the same caliber are the same price), 3.5# connector, extended controls, and HOLE in the slide lol are worht the extra coin. Ultimately, to me, the pr9ice diff is not a big deal (same when considering sig ftm), because you'll end up spending many times that difference in ammo for the life of the gun. Give them all a try.
So, since you already have a 19, my vote is 34. Any advantage you would have had with the 17 (over the 34), is covered by the 19 imo. You still get mag compatability w/19, get a little more sight radius which does help at longer distances, and don't ahve to worry about the "inconcealability" (to some) of the longslide, because you have ccw covered w/.your 19.
Whatever you choose, it's win-win.
