I enjoy my hk usp 45 and I own many 1911 I'm assuming its about the sane recoil. As far as feels different is it uncomfortable.
Size-wise, it's barely bigger than the 17. Unless you held them side by side, I don't think you'd know the difference. Recoil is different than the 9mms, but not really any more difficult to handle, especially if you were shooting defensive loads in the 9mms. .45acp just feels different.
I've always felt concealed carry to me was no one knowing you have a gun on you. If they know you have a gun you have already list 1/2 the battle.
My only experience with that size of a glock was with a G20. They're identical in size and for me I would never consider carrying something that big. I don't see the reason behind trying to carry a full size gun when so many quality compact and subcompact guns are better suited for carrying. If you want one just because then that's a different animal.
Totally valid, but my train of thought is different. For me, I don't see the rationale for carrying any less gun than you are able to carry. If that's a Nano, so be it, but if you CAN carry a full-sized gun, why would you NOT carry a full-sized gun? If a voice spoke to you from the darkness in the night saying, "Tomorrow your life will be in danger, your family will be threatened, and you will be in a gunfight", what gun would you take? That's the gun you should take every day, if you can. If not, step down that list, in order, until you get to the first one that you CAN carry. Not the one that's most comfy, or the one where you're betting that you won't have a problem, but could give it a shot if you absolutely had to -- the one you'd want in your hand if you had to protect your kids today. I think a G21 would be a decent choice.
YMMV.