Buy whichever feels more comfortable to you. Both are great guns and reliable too. IMO Glocks are more reliable and have a much longer track record, which is enough to win me over. When in doubt, a Glock will almost always function. They aren't perfect but, they are about as close as a handgun gets to being able to be treated like a lawnmower and still keep running fine.
Aside from the time frame, all the same points can be made for the XD.