I have the PX4 in 9mm and really enjoy the gun. Before buying, I was looking hard at the XD9, hard enough that I convinced my son (a pastor with a 3 year old daughter) to buy the XD with a 4" barrel.
The XD has the grip safety, rather than a decocker. There are a lot more choices out there for holsters for the XD than there are for the PX4. Personally I shoot the XD more accuartely than I do the PX4 (although I still love the gun).
There is no BAD choice. As mentioned above, buy what feels good, what you enjoy shooting the most. You will be buying a second gun eventually, so don't sweat it.
As far as price, sometimes we sacrifice price for freindship. Its up to you to decide how badly that pastor/parishner relationship will be hurt if you get the gun from a discount store. I sometimes pay too much for a gun at my range because I know I will get more back from them in goodwill and "extras" than I have lost in not buying from a competitor. Other times, I just go to the competitor. They are still happy to see me when I come through the door.
In the meantime, no matter which gun you buy, do what you said; keep the gun in the safe or use the lock that comes with it when you don't have it on you, and keep it away from your kids. Those are the only safety measures that really work.
Never argue with drunks or crazy people.