Do you dissaprove of the recoil on your xd? If you think the muzzle points too far up after each shot, and it tweaks your wrist, go heavier. If you feel the muzzle stays low but your getting shoved around go lighter. Trigger do you need/justify a better trigger? Its all in what your using it for.
I'd say go to dons guide rod forum and ask him, he knows everything in life. It all comes down to feel in reality. I've seen a guy with a sigma outshoot guys with kimbers, just because he had better control.