I carry a Glock 26 every day, and have for about four years now.
My husband got an XD-9 for Christmas, and has been carrying it since then (yay!)
When he was looking for his carry gun, I urged him to try the G26 first -- so that we could share equipment such as spare magazines, mag pouches, holsters, etc etc. He shot my Glock a lot, but simply never warmed up to it. The first time he picked up the XD-9, he positively raved about that gun, about the way it felt in his hand, about how much better he could shoot it, about the better grip angle compared to the Glock.
Well, hmph.
Me, I still love my G26. It is the perfect size for my hand, I like the grip angle, and I love how concealable it is.
The longer grip of the XD-9 may be better to shoot, but it is much worse for concealment with the rig I use.
The shorter barrel of the XD-9 means that there's just a little less oomph coming out of the end of the gun -- maybe not enough to matter, but if there's going to be a tossup, I want more oomph.
And that grip safety! For crying out loud, what's the deal with that? If I'm in a firefight, I may be gripping the gun as hard as I can (no problem there) -- but if injured in any way, perhaps just perhaps I wouldn't be able to activate the gun because of that grip safety. Sure, lots of people trust their lives to such a system, but ... y'know, I just purely love the simplicity of the Glock.
Bottom line? Go with what works for you. Both of them are excellent guns, both will put shots where you want 'em as long as you do your part, and both are defense-caliber weapons in acceptably concealable packages.
pax