I have, and love, two Glock .45s. I have a G-36, which I carry constantly, and a G-30 which is a great gun also, and my nightstand arm. Both have been flawless, and the 36 is a bit easier to carry because it is thin (single stack 6+ 1 the 30 holds 10+ 1).
Many people carry the 30 with no problem, and the rail on the frame allows for a light attachment. (36 has no rail). To me, the XD grip sticks out too far and shows under a shirt.
The best bet is to try to rent them, and see what you like. You won't go wrong with any of the three, but, I think the edge in concealability goes to Glock-36.
My favorite Glocks: