The shocks/springs are better for offroading. It has nothing to do with travel.... did you ever take those measurements to see how much down travel you have with the spacer lift?

I upgraded to OME because my stock springs were sagging really bad with the added weight from skids/equipment. Also the stock shocks noticeable allow the body to drop lower when going off obstacles which decreases the effective belly clearance. I think for on-road ride quality the stock shocks are slightly underdamped whereas for off-road performance you want slightly overdamped.