I think Google Ads is more complicated based on the breadth of knowledge required.
With Google, you need to be familiar with both Search and Display advertising while FB is predominantly going to be Display. SEM is a completely different specialism altogether from Display so this alone IMO already makes it so much harder.
Google also has a larger selection of channels available that are based on my experience, all pretty decent (Search, GDN, YT). FB family of apps is still going to be mainly FB running the show with IG coming in for certain markets/demographics.