I would say you are going to be better off going with the 45.
You are going to need to shoot the thing and practice. It is
a lot easier to find 45 ball ammo to practice with than cheap
10mm ammo. And if you decide you want to trade it or sell it
a 45 is going to be a lot easier to find someone interested in it.
Having said that, buy the one you want; they will both kill
deer. I've shot deer with both calibers and they worked well.
You just need to know the limitations of the gun and yourself.

And if you are new to pistols I'd suggest you buya good 22 pistol, a couple of bricks ammo and shoot the heck out of the thing. 22s are so
much cheaper to feed, and great for getting the basics down of sight alignment and trigger control.