To the OP..The only way you are going to find the pistol that you should get is by getting your hands on them. Both Glock and the XD are quality weapons and can serve you well. Glock professes the lower bore axis that is supposed to decrease felt recoil. Owning both pistols in more than one caliber I can say truthfully that there is nothing in Glocks bore axis that allows for less felt recoil to me. Glock also has the milti safety safe action system. All of this I find puzzling being the reality that the only true safety in this system is keeping ones finger outside the trigger guard. The Springfield has the passive grip safety that also really doesn't mean much once the weapon is in your hand. What both these weapons do have is a record of reliability. TRue theGlock has been around a little longer but I can't honestly use that as a point of reference with the never ending battle with Glock fans and 1911 fans being the 100 years of reliability the 1911 has is a moot point with Glocks supporters. Bottom line is the weapons you are looking at both have a good record of reliability. It has to come down to how it feels to you. Both Glock and the XD system have a very different feel. Either can protect you and do well at the range. But only in the hands of a shooter that feels comfortable with the pistol.
AS to caliber..My 19 year old daughter shoots all my 45's. She's about 100 lbs wet. While It's not the best for everyone it's not a whole lot to get used to. The lower pressure 45ACP's felt recoil will be more in a lighter frame weapon like a Glock or XD. But, it's not so much morethan it makes the weapon hard to manage.
I hope yo find your new friend soon and the choice you make leaves you happy with that decision.