Glock 17, 3rd Gen current production: Simple, proven, very reliable action, high capacity, user-replaceable parts, very affordable factory/reliable mags, primo slide finish.
G17C: fine for shooting in competition, but not my choice in carry gun. The 9mm is not uber powerful, and I want all the cycling power I can get for real-world applications. I spent several days shooting next to guys with 22Cs. The muzzle flash at night, with duty ammo, was NOT night-blinding. However, I did get some projo shavings and pressure waves blown my way (canted pistol for firing around barricade). Not fun if you're not wearing full eye protection. But, like I said, if you're a gamer, go for it. Every little bit helps, eh?
XD series: Simple, very reliable action, mag capacity a bit limited for the size (My G23 holds only 1 round less than the full-size, non-tac XD-40 I owned), an overly-tall grip and slide not conducive to concealed carry, non-user-replaceable extractor, poor slide finish (almost like parkerizing, and wears off easy), cannot rack slide without fully depressing grip safety, mags more expensive than Glock but very reliable, trigger geometry/design wears sore on many shooters.
After owning both, my choice is the Glock. Sold the XD, as it was just too bulky for anything but home duty, and my duty and personal weapons are Glock. If the XD fits you much better and you actually shoot much better with it, then the choice for YOU is obvious.
Just curious... does the slide still have the "Made in Croatia" rollmark on top, just in front of ejection port?
-josh