Because all the parts are available online and their fixable w/o mailing the gun back to manufacturer for a minor repair.
Don't be afraid to buy a used Glock sub-compact either. They just don't wear out. If you do find a worn part in a used Glock, just replace the part and keep shooting. Fine weapons...
i had the same decision to make and went with the glock. reasons: 1/2 inch longer barrel with same slide legnths and shorter slide height making it more balanced. to me this makes it seem better engineered. mine had been 100% reliable with over 500 rounds down the pipe and very accurate especially for a small gun
I've had the XD sc and it was a very nice gun for the range, but after I became comfortable with carrying a gun and taught myself to draw with my finger outside the trigger well, I didn't think I needed all the safeties. However, I continued to cary it for a while and soon the safeties became annoying. Besides the Glocks have enough safeties.
Bottom line, you have to choose and carry the one that you will trust with your life and those of your family members.
I've had both and prefer the XD. They are both good handguns, but I like the feel of the XD better (the grip angle and grip safety remind me of my beloved 1911s).
You need to try them both, then decide which one you are most comfortable with. After all, you're the one that will be carrying it and trusting your life to it.