Orr might've had the highest ceiling, but Howe's numbers are staggering over the course of an absurdly long career. He played in over 5 decades. The early years(40's, 50's, 60's) during the original 6 era were when points were harder to come by.
Keep in mind that he was also a ferocious physical presence in all areas of the ice. Even older members like me never saw him during his glory years in the early and mid 50's. I remember him in the mid 60's(during his mid late 30's, when most players had retired, back then), often finishing in the top 5 in scoring, and cruising around the ice relatively untouched. I thought it was because he was so respected(there was no doubt back then that he was a Superstar), not realizing that other players were petrified of making him mad.
I don't know who was the better player, because I never saw Howe in his prime. I do know that Howe had the better career.
Orr was spectacular, and I would take him any day over Lemieux. He would skate circles around him. Hell, I'm not sure that a young Beliveau wasn't Lemieux's match. It was a different game pre expansion, with much tighter defense. Very tough, also.