Personnally, I like the .40, wife likes her .357 mag. So like most have said, if the gun fits you and you are comfortable shooting what caliber you choose, then go with it.
Here are a couple of sites, very informative and like here people are all over the map in caliber and model. But that is what makes it interesting. Just like the old geezers 1st gen bike vs the whipper snapper 2nd gen.
http://www.xdtalk.com/
http://www.carolinashootersclub.com/forum.php