I’ve received more questions about this topic than any other topic, ever. Some say the Shield is thinner, others say the XDs is bigger and heavier.
As far as overall size, the two pistols are really close. I took a picture of each pistol (same focal length and all that mumbo jumbo) and laid them on top of each other. I lined them up by the back edge of the front sight, and they are pretty darn close in overall size. The XDs does feel a hair heavier, but we’ll break out the scale later and put that to rest.
You will also notice the bottom part of the picture shows the thickness of the pistols. Unfortunately both manufacturers felt the need to add levers that stick out pretty far from the slide, which makes the gun on the right hand side look thicker. When it comes down to it, there’s no practical difference in the thickness of either pistol.