Be critical of yourself beyond your time. Are you honestly the type of person who has the fearlessness (sometimes recklessness) to start a new company? To commercialize research? To wait for decades before your net worth recovers from the risks you've taken with it? I get that an MD has a similar payoff horizon, but the way you get back to zero is a lot less uncertain. Medicine attracts the conscientious and encourages structure. If that's you, why deviate from the plan?
Is the knowledge you get from b school worth it? No. Of course not. You could read and understand and apply any part of the curriculum you needed in no time. GAAP, NPV, WACC, capital markets, channel marketing, securities, leverage... you name it, it's learnable. Don't be one of the people who go to b school to learn the material. It's trivial.
Are the results worth it? Certainly. I didn't grow up around many families with dynastic wealth, so YMMV. But going to a top 15 MBA program meant that I had regular lunches, cocktail parties, tailgates, and lectures with folks with $50M+ net worth. That mattered when I started a capital-intensive business. Even if it's just their names on a business plan, or their willingness to back a loan agreement, the terms and tenor of bank or investor deals change noticeably. But does it matter if you don't need those kinds of things?
Peer connections help immeasurably, too. Core groups of students at b school can get incredibly close, and I have lifelong friends (all highly motivated and bright) in almost every major industry. Get a Bain or Deloitte opinion in 3 days for no cost, or a BOA/Honeywell/J&J board member on the phone in 24 hours. If you need the capital for starting down the horrendous drug test pipeline or if you're a hospital system CEO who wants to acquire another hospital, you'll be glad to have your Alta Partners or Goldman rockstar number handy. But would you care if you never met them or needed their help?
It's also a bullet point next to your other experiences, whether on a loan application for financing the working capital needs of your clinic or a board bio for a publicly-traded company or if you're gunning for city council. Those things matter in a way you wouldn't expect from just knowing the course material. It's a belief and a trust like the kind you get with your MD, but for a very different purpose, and with a very different reputation. The combination of both will be interesting to a lot of people. But are they critical to where you want to be?
Is the attitude you develop worth it? That's on you. You think about money a lot differently after b school (one person's opinion). How little it matters. How easy it is to find if you have a compelling idea and a solid team. But it also squeezes a little bit of humanism out. You see just how exploitable humans are. And you can more clearly see the systems that do it. Are you prepared for that?
Many people get MBAs because they don't know how to advance their own careers, or they want to change industries or levels of responsibility. Most of them end up as dead-end, middle managers at GE, IBM, whatever. Filler. Fewer are the ones who will use a new degree to get their foot in the door of a stretch job, dominate once they're there, and rise prominently to the top levels of their field. Every field has those types. Are you one?
If you're asking for us to tell you which one you are, you're the filler. Play it safe. Finish MD, do your duty, retire with a decent 401k and go golfing. You'll be a local hero to a lot of suffering people who needed your help. Join the rotary club and pay your dues. It's a fine life.
If you're asking us to see what your best option is so you can kick down some doors and dominate, it's worthwhile investment. If you go, go to the best school you can get into. One with a robust alumni program (HBS, Dartmouth, Yale, Notre Dame, Stanford, Columbia, etc). Then, go make a mark on the world*, donate enough money to build a hospital with your spouse's name on the plastic surgery wing, and pay it forward to the business school alumni network so the next starry-eyed kid can have their shot. It's a fine life, too.
*obviously, getting an MBA doesn't mean you'll be this and not the other. Like I said, plenty of dead-end MBA jobs with MBAs to fill them. They make a good salary, and that's all their ambition or talent or creativity will ever get them. Your MD is already good enough (or better) for that. There is no need to get another degree that gets you the effectively same results.
tl;dr: If you're going to be a clinician or run your own clinic and then go golfing three afternoons a week, it's not so necessary. If you have the stamina and mindset for a completely different type of life, then it's a good tool to have. Nothing guarantees phenomenal success, but don't waste time and money doubling down on the obviously tried and true path if that's only what you ever wanted in the first place.