Cons

Tuition cost and opportunity cost of work

Getting another degree is an amazing opportunity, especially if you can save an year of time and tuition when doing it in a dual degree program. However, when compared to doing a solo-MBA, the added cost of another year of school (in the case of a three-year program) can be daunting. You'll have to pay ~$60k of tuition and fees and forego one year of salary at the starting MBA rate ~$125k. That's a large chunk of money to make up over the course of your working career. Of course, MD and JD students who have already prepared themselves for the long-slog of school see the marginal cost as relatively lower and the benefits of the additional MBA on their future careers is great.

Unintegrated program means extra work of building your own path

Unlike integrated "joint degree" programs where academic deans have established well defined pathways for pursuing two degrees, often bolstered by a steady pipeline of concurrent degree students who can help show you the way, unintegrated programs mean that you have to fend for yourself. If you're not the kind of go-getter who can coordinate with two different sets of graduation requirements and two different registrar offices, this option may be a little stressful.

Takes time away from your MBA cohort

Depending on when you sequence business school in your dual degree program, you may not graduate with your MBA class or spend much time with them after the core curriculum part of the degree is over. This can be a serious downside considering that the network is a key part of value proposition in MBA programs.

Shuttling between campuses

If you decide to do a concurrent degree at two different schools, it is likely that you will have to pack up your apartment and move at least twice in a three year period (notable exceptions include the dual degree program between MIT Sloan and Harvard Kennedy School). For ex-consultants, living out of a suitcase for three or more years might not sound so bad, but for the rest of us this can have a negative effect on quality of life. Even if you decide to pursue two degrees at the same university, graduate school campuses are rarely co-located and so even if you keep your apartment, you still will have to shuttle back and forth across as variable commute (notable exceptions include programs between Harvard Business School and Harvard Kennedy School, which are located just across a walking bridge from each other). Of course, if for some reason you would like to be in two different cities over the course of your study (e.g. to be close to two different sets of family, you didn't get into the desired program in your #1 city and are using a dual degree to form a back-up option), this can be a blessing.