Also med student here.

I've been struck with the same question, then I came to realize that if there ever is an AI that can replace a doctor, then they would also be able to replace pretty much everyone else. Imagine there's a medical robot that could perform surgeries: It could learn how we are anatomically, how to spot conditions, how to surgically treat them, etc. If properly maintained, it would be more accurate than a human ever could. Then again, if there ever was a machine like that, what it wouldn't be able to do? So, there's not much sense into trying and figure out what specialty to choose based on if it's most likely to be replaced by AI or not. Still, if you're going that way: Any surgery field, Psychiatry, Neurology, Anesthesiology.