This feels like it should be obvious, but the advice I’d give anyone who had to make this choice for real will sound quite counter-intuitive.
Based on what little we know about the two surgeons, I’d pick brain surgeon B.
Why?
Because of the psychological mechanism called the Dunning-Kruger effect. Put simply, the Dunning-Kruger effect says that people who know less about a subject tend to overestimate their skill in that subject. At the same time, those who know more about a subject tend to underestimate their skill in that subject.
So brain surgeon B may be the better choice because they know they don’t know everything about brain surgery and are always looking to expand their knowledge, keeping up with the latest discoveries.
Brain surgeon A may have convinced themself 10 years ago that they’d learned everything and could be completely unaware of the lastest advances in the field.
I illustrate the Dunning-Kruger effect in a more colourful way in The Lies That Divide Us, right after the bit where I demonstrate a simple technique to help us make more objective decisions, using the GTH Question simulator, ex-UK PM Boris Johnson and a sock puppet duck.