My advice is to stick with OEM. My Monza shadows are in perfect condition (get washed every week) and there is no white worm. Reps are normally much heavier and I have heard (no experience myself) the increase in unsprung weight affects the steering and handling.
One of my neighbours has a Golf with Monza Shadow reps and from a distance they look good but close up the finish is rubbish and they are corroded now.