I can’t find a reference to the statistic but I have often heard that if the captain is the flying pilot, thern an accident is more likely. The speculative reason is becaue a copilot is less likely to challenge a captain when things are not going well. Conversely, when the captain is the monitoring pilot, she is more likely to say something and be heard by the copilot.
I wish I could find the source of this information but I’ve heard it so often, that I believe it’s true.
In my own experience, I think that the tendency for captains to be more assertive is very, very prevalent and that’s why it’s incumbent upon the captains to level the “authority gradient” and work hard to be approachable and open to suggestion, guidance and challenge. Not only will the flight be safer, but the crew will work better together and a crew that feels appreciated will almost always work harder and do more.