The amounts of offset on the intake rockers is the difference.
In terms of "stamped" or "steel/aluminum rollers", I will take rollers every time. The stamped steel will flex. at small spring rates (say 350lbs open) you can watch the rockers flex. They last, but they lose lift on every flex, and they are heavy compared to aluminum rollers. Plus, available ratios are better, and the ratios are more exact. A 1.5 satamped steel rocker is really somewhere between 1.5 and 1.4:1 True roller rockers, and the better race versions, are available to 1.7:1. Which can be very advantageous when selecting a cam. Now, rollers are not created equal either. Very simply, anything under $400 new is probably trash, and no beter than stamped steel. Scat, Proform, Scorpion, all fall into that last category. If you run them, they are a waste of money IMO and may be hurting you. Crane is the bargain one.