In my experience, powdercoating has withstood rocks, gas, oil and environmental exposure better than paint. I have not seen powdercoat chip unless you drop it against the ground, hit it with a hammer or other hardened implement -- but that's just me. As Mick says, everyone has a story. . .
FYI - I painted my last engine with VHT paint because (then) beadblasting and powdercoating the cases was a pain in the butt to make sure all of the media was cleared out.