I have the original XDs45. I plan to add a 4" XDs9.
I really like the XDs platform. It's the perfect carry gun for my tastes and demands. If the 4" seems to fit just right, I may sell my 3.3" 45acp...and it may be replaced with a 4" 45acp.
Perhaps I haven't figured out what's perfect just yet. But a single-stack 4" subcompact sounds pretty ideal to me. I also like the S&W Shield a lot (had one, but the XDs bumped it off). But the thumb safety is a pain to de-activate, and I prefer the grip safety on the XDs. Being a bit of a 1911 homer, grip safeties are no deterrant.