Can't offer any first hand insight as I have never owned either of the subject pistols. Having carried handguns for over 40yrs for personal protection and for a living, I can offer some general observations. Thin and light are where it's at for concealability. The SR9 appears to be a little thinner and less blocky than the XD, probably a little lighter too. Both are double stacks so they are still a little thick for concealment wtihout a cover garment. There are better choices from a concealability standpoint, but as you are not open to other options I won't bore you with them. As a defensive handgun, either one of your choices would work well.
Savage