There is an important distiction: Equifax's data is not voluntarily submitted by the data subjects, while most of Facebook's is.

Equifax is also not under EU (GDPR) jurisdiction afaik.

That sounds worse for Equifax

Although I don't see this having a huge immediate impact on Facebook, the distinction is that if Equifax neglagently releases your PII there is little fallout as you are not the one providing Equifax with that data and cannot simply stop feeding them data, when Facebook does it their data subjects can choose to stop providing the data by exiting the platform. Facebook needs both the user data, and those same users patronizing their service to maintain the existing revenue stream.

Precisely.

The personal communication stored in Messenger is materially different. Affairs, criminal activity, talking about the boss... This has the potential to actually destroy lives.

The general public don't have a clue what Equifax is and don't know about the hack. Your Grandparent's sexting convos being put online might grab the public's attention a little more.