I am not a Glock fan, but it was the larger grip frame of the G21 that made me realize I needed a polymer frame .45 ACP. That was a good many years ago and I actually waited until SA released the XDm 4.5 in .45ACP and mine is perfect for me.
Before you buy a Kahr CW45, I would check out the SA XDs in .45 ACP. People that have them, love 'em. And as far as customer service goes, SA can't be beat.