Choosing your thesis committee is basically academic Russian roulette. You've got nine brilliant minds here, but only one will actually defend your work while the rest sit in judgment, picking apart four years of your life with questions like "Have you considered [obvious thing you dismissed in chapter 2]?"
The real challenge isn't writing 200 pages on obscure knowledge that three people will read—it's surviving a room of professors who've forgotten what it's like to be sleep-deprived and surviving on ramen. Choose the wrong committee member and you'll be doing "minor revisions" until retirement age.
Pro tip: pick the one who naps during faculty meetings. They'll sign anything to get back to their afternoon coffee.