Different energy. Bus driver has to deal with many potentially grumpy people in many potentially unsafe areas. Not an easy job.

A doctor that is specifically specializing in a field where he has to get to know and take care of children as they die in a potentially painful way, has a much different challenge. Less for safety or aggressive people (though maybe parents could be I guess) but more in being the one to watch as the hope fades for each individual child in their last days.

I wouldn't love the bus driving job. I don't think I could do the pediatric oncology one for more than like, one patient ever. I'd be depressed forever.