SCT versus random orbital sander?

I'm no body man but as i recall from my best friends dad who was when I was 16ish, a D/A is not the best thing to use either. He used a 7 or 8 inch grinder with a 60 grit disc and no backer. Ripped the paint right off. A D/A can heat the panel or some such thing. Obviously don't stay in one place too long. Long sweeping movements.

Hopefully someone more qualified than me (literally ANY bodyman) will chime in and set us all straight.