As someone who has gone from engineering grad school to law school and then got an MBA, I can't say I would recommend the MBA unless you do not have any technical skills or have no sense of direction when it comes to basic business and accounting concepts. If you can read a 10K report and get a good idea of the health of a company, then you will be more competent than many MBA graduates.
In addition, there are so many MBA programs out there that are basically scams to separate you from your money. Your MBA will only be as respected as the school is. As many of the comments allude to, the main purpose of the MBA is to network and show employers that you are ready to "play the game." Your mileage you get out of the degree (when it comes to employment) is pretty much directly proportional to the rank of the school.
However, there are some instances where an MBA makes sense. Sometimes, individuals looking for a career change or to get an internal promotion/raise will use an MBA program to pivot since it gives you two years to make a seamless transition on your resume.
If you are looking to go back to school to obtain some skills to better build your business, I would recommend going to law school over getting an MBA. From my personal experience, I would say that law school provided me with more pertinent information about running a business than my MBA. While law school is far more rigorous than an MBA program, it would certainly be worth your time if you can get the score to get into a good one. There is a reason why many successful founders have law degrees. I think it is because law classes teach you not only to think clearly but also to think about contingencies -- skills that are essential to building a business. You will also be surrounded by intelligent, hyper-driven people which creates an interesting atmosphere, to say the least.
