I love the 3" XDsc in 9mm. In 40 it is a bit more recoil to tame - some people are fine with the extra recoil, some have an issue with it. The 3" XDsc 9mm is capable of group sizes about 2-3" @ 25 yd.
I also have an 4" XD compact which is comparable in size to your glock 19.
My experience has been that the 3" gun is more versatile since it has similar accuracy, is easy recoil to handle, and is much easier to conceal than a pistol with a 4" barrel with longer grips. If you're simply looking for a duty gun and concealment isn't much of an issue I'd stick to your G19.
I also have an 4" XD compact which is comparable in size to your glock 19.
My experience has been that the 3" gun is more versatile since it has similar accuracy, is easy recoil to handle, and is much easier to conceal than a pistol with a 4" barrel with longer grips. If you're simply looking for a duty gun and concealment isn't much of an issue I'd stick to your G19.