Q: How does this compare to just replacing worn parts with factory arms?

Stock replacements return you to the original soft-rubber, non-adjustable setup that wore out and limited alignment in the first place. This kit upgrades the bushings to sealed spherical units, adds ball-joint improvements, and builds in more than 3 degrees of rear camber adjustment. So you get a car that is tighter than a fresh factory refresh and correctable at the alignment rack, where stock parts only return you to baseline.