First off, welcome to a GREAT forum. I'll start by saying that 9mm is sufficient for a defense load. I have shot Glocks and own 2 XD's now. The Glocks have a lower bore axis which some say creates more muzzle flip in the XD's than the Glocks, but it's not sufficient enough for me to notice a difference. As far as the recoil being worse in the Glocks because of it's weight, I also don't think that it's enough of a difference to make it noticeable, especially to a newer shooter. Both are very reliable guns and I don't think you could go wrong with either. If money is an object, you can find XD's for quite a bit less than the Glock's, but if not then I wouldn't make money a deciding factor. If you can, I would suggest trying to find somewhere where you can rent them and shoot them both as that would most likely help you make your decision more than anything else. If you cannot rent and/or shoot them both then I don't know what more to say I hope that helps a little. More people with more experience will be in with more input for ya.
Edit: I forgot to add that 9mm is also quite a bit cheaper to shoot than 40S&W and 45ACP