I don't own a Kahr KP45, but have handled them. I do own a PM9. I've never handled S-A's XD's, but unless they came out with a new sub compact .45, it's nowhere near as small & light as the Kahr, right?
Another gun you "might" want to look at is Taurus's Mil Pro PT145. It's heavier & a little larger than the Kahr .45, but it holds 10+1 with a lighter trigger. It's basically like carrying a slightly shorter Glock 26, but a .45.
Anyways, nothing's wrong with either gun, but there's quite a difference in size & weight between the Kahr KP45 & SA XD45c, I think.