Sorry I am late to the party. I am one of those 10mm lovers. Sorry but this is going to be long.

If you only own one handgun it shouldn't be a 10mm. As for 10mm or 45acp I own both. Let me break it down for you a little.
Yes it is more powerful then the .45acp. Yes it does have more recoil then 45acp+P but not that much more and this only holds true to loads from companies like Underwood or Buffalo Bore. The watered down stuff is just like shooting .40 S&W. It is a good handgun hunting round IF you do your part on game up to elk. My dads friend regularly hunts bull elk and has taken 2 with a similar setup like mine. Glock 20 6inch barrel. From a 6inch barrel the hot loads are about equal to medium .41 mag loads from a 4inch barrel. I have taken mule deer, white tail, javelina, wild hogs with clean one shot kills.
As for concealed carry or personal defense I don't think the round has really anything over the .45acp or .40 for that matter. To me .40, .45, 10mm are all about the same in the personal defense from 2 legged creatures. FYI, I also own a Glock 27.
I just got back from two academys tonight just to see how bad it was. I have been sick for 3 weeks and haven't been to a gun store or anything in weeks. WOW! At the Academy in Tomball the only handgun calibers they had were 45 LC and 10mm. I laughed so hard when the clerk said they had nothing but odd calibers. Same thing happened in 08. No ammo but I always remembered seeing .45 GAP.
As for 10mm becoming less popular? I would say that is dead wrong! I never saw 10mm on a counter 4 years ago when I first got my Glock 20. Now even if it is the watered down .40 S&W loads you can find it at all of my local academys. I asked my local shooting range and they said that over the last 5 years 10mm spent brass is way more common. People are shooting it but if you haven't noticed yet all the good stuff comes from online dealers. Underwood being the best bang for the buck imo. Right now they have no ammo. I bought it all a month ago!
Anyways, unless you going backpacking out west a lot like me their is nothing the .45acp won't do for you in Texas. I have dropped all the game I mentioned for me with a .45 except the mule deer. On bigger game the 10mm will be better for hunting or protection from black bear or moose but it is no .44 mag. Just a powerful semi auto and probably one of the most versatile ones at that.
Long story short buy the .45acp first unless you plan on going hunting, camping or hiking out of state. In Texas the .45acp is enough.