Law was great, medicine for me is better. However I suspect your dad has an over glamorized view of medicine, how little certain specialties deal with people, etc and is suffering from grass is greener notions. The practice of law and medicine have a lot of similarities -- at their heart they are both hierarchical fields, with lots of paperwork, politics and liability risk, where you leverage your knowledge and provide a service to a client -- and so if you have frustrations with one, you'll often have similar frustrations in another. You aren't going to get to stand in an OR or sit in a dark room all day and marvel at the wonder of the human brain.
I've also seen enough medically related law cases to know that it's really how little lawyers actually have to understand to work on these cases is what's really the astounding part. Your dad probably THINKS he learned a lot, while his expert likely goes home thinking "I've dumbed it down as much as I could -- i really hope he understood enough of it to get by, because I have my doubts, based on his glazed over eyes and poorly thought out questions "-- And that's not an insult to your dad, but a reflection if how deluded most lawyers are, and how little science most understand. I was one at one time and as much as you'd like to pretend you are learning things, or have enough of a foundation to grasp difficult medical concepts and be able to talk competntly during your case, there's really only so much you can absorb from experts or teach yourself while preparing for a case in any field that requires four years of med school and nearly a decade of residency and fellowship (in the case of neurosurgery) to master. The way an adult explains difficult concepts to a two year old is pretty analogous to the way a neurosurgeon has to explain neurosurgery to a lawyer. And again this isn't an insult to the lawyer -- he's just not got the requisite schooling and training as foundation to receive this kind of info. Like law, in medicine, all your value and stock is really measured by those areas everybody doesn't already know after a single med school course, and those things that take years of training to even comprehend. Which is why anyone patting themselves on the back as "amazing how much they've learned" in just a couple of hours of case prep on a brain injury case is kind of amusing.