I would add a remark in regard to the value of leaving graduate school with more than one skill. Specialization is good in general but you want a bit of insurance against sudden changes in disciplinary enthusiasm for particular tools or styles of work.
Whatever way you go, remember that you need to be on tomorrow’s frontier, not yesterday’s. If this sounds anxiety-producing, it is. Angst and anxiety are the fertile soil from which dissertations grow.
If you think that sounds miserable, wait until you start thinking about your tenure packet.
Actually, it’s only miserable in the worst moments. Most of the time it’s exciting and rewarding. You get out of bed every day and push your brain to its limits. Those limits expand a little bit every day. People will eventually pay you to do this, even though you would secretly do it for free.
Ultimately, you should be doing what you love. If you don’t love it, chances are you won’t be any good at it. So keep that a first priority. But pushing yourself to the frontier is often rewarding for its own sake, and pays off in your academic career. Try to keep that in mind during the most anxious, vexing moments. I do.
This piece also reminds me of my former colleague Ig Horstmann, who told one incoming class of graduate students at Western Ontario that "I wake up every morning and think `Thank God I am an economist'". I second that emotion.