Isn't Pornhub's content always public, whereas Facebook's can be segregated to smaller groups of people? If that's the case it seems that illegal content could remain undetected for far longer on FB rather than Pornhub.
I’m not an expert on PH, but from what I understand from other sources they have a mix of public content, open-to-all-paid-customers content, and private content that is available only to subscribers to particular channels.
I don’t know if they have any content owner (well, submitter, given the level of piracy) controls on who can see content at the specific user level (whether by restricting allowed subscriptions to channels with an owner-approval process or by having content restricted by something other than subscription status.)