Ph. D., mathematics.
No comparison. None.
To an extent law is still a trade, but navigating law school requires good cold memorization skills and the ability to make connections between apparently unrelated groups of facts and theories. Plus of course you have to be a good persuasive writer. And be able to synthesize a bunch of memorized case law into some kind of presentable legal theory in 3 hours or less.
Just looking at Obama and listening to him talk tells me that he never did as well in law school as everybody says he did. He lacks the "think on your feet" skills that let you write a good exam in three hours when you can't really remember all the facts of Pennoyer v. Neff.
Practicing law is thankfully a lot easier than law school (and it certainly is easier still since LEXIS and WestLaw came in). But that brings in a whole new group of skills that you don't learn in law school -- 'reading' a jury panel, cross-examining a witness, writing a persuasive appellate brief. The really good guys are born with those skills, but they can be learned by experience. And again, it's obvious from listening to Obama that he never really did this work. Lawyers are like sharks when it comes to sensing an inexperienced tyro thrashing around in water out of his depth.