Tough Choice: Both are the cream of the crop of 9 mm Luger pistols. Honestly, if you can afford it, get both. If you have the chance to handle both, pick the one that feels more friendly to you. The DA trigger of the Sig-Sauer is a bit of a challenge at first, but it can be mastered with sufficient practice. For some shooters (including myself) blessed with smaller hands, trigger reach in combination with a double-stack frame might be a problem with the Sig-Sauer. Sigs seem to be somewhat more accurate than Glocks, but for practical shooting the Glock does well enough. The Glocks I've shot were models 21, 22 and my personal G17. Trigger reach is no problem and muzzle flip/recoil, especially when the Glock in question is chambered for the 9 mm, is easily controllable. The Sig-Sauer rides somewhat higher in the hand, so muzzle flip seems to be a bit greater, but not enough to be bothersome for quick and accurate shooting.
Personally, I prefer the Glock because trigger reach is shorter than that of the Sig. If I would purchase a DA auto pistol today, I'd always choose the Sig-Sauer P226. I have never done this because of the personal matter with the hand size.
In the shooting club where I am a member, we also have three guys from Germany's Sigarms "Standard" and "Production" IPSC team. They're using the all-steel P226. The initial shot in DA mode doesn't affect their shooting negatively anymore, but it took a "few" rounds to get the ability to fire a Sig-Sauer as well as their SA or "Safe Action" autos
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Honestly, both the G34 and P226 are top-of-the-line production handguns and I am confident you'll love either one.
All the best.
TK