Which branch sets you up the best for a future MBA?

None,
I know this sounds brash, however, your goal should not be an MBA. Your goal should be to join and become a successful and servant leader. Make sure you look into ROTC otherwise you may have to go enlisted regardless of education level. We have helped many a young successful Soldier with a degree get into the officer "Green to Gold" program. Getting back to the original thought, the follow-on degree should not be your primary goal. Serving and being successful in whatever career field should be your goal. Also, understand you may not always get your first branch of choice. Often the Army or military will choose the branch you go into. Regardless of the branch, the skills you learn as an officer will be of a value seldom achieved anywhere else in the civilian world. Good luck in whatever future endeavors you choose.

I don't believe that you are going to find a specific branch or even MOS for that matter that will do anything special for you in regards to preparing you for an MBA.

The branches are basically immaterial. All provide opportunities to lead, which forms a base of relevant experience for pursuing an MBA. The functional areas are a more appropriate guide for development in business-related areas. Unfortunately, the MBA is often a prerequisite for moving into many of those functional areas.

The MBA curriculum doesn't assume you have a business-related background. They teach all of that from scratch. Given that you are coming in with an economics background, as well as a more quantitative foundation (from the CS curriculum), you will be just fine. Most programs draw students from all across the academic spectrum (math, sciences, liberal arts, business, etc.), so you will already be ahead of many of your peers. I would just focus on doing well on the job in whatever branch you pursue, and then prepare for doing well on the GMAT (or GRE, which many business schools also accept these days).

Whatcha Branch? They are all the same if an MBA is your goal. That is because none of the services are business. They are government agencies/departments. You may learn some leadership traits which may be helpful beyond what you need to learn for an MBA. So they are all as equally worthless or worthwhile which ever way you look at it.

I did my MBA work after hours and on weekends while I was stationed stateside. I was an Army officer in San Antonio at the time. But most of my classmates were Air Force.

Everyone has their own personal bias because of the branch they’ve joined. In my opinion, the air force would probably do well to you. They most likely have the most translatable skills in the field you’re in. The army would probably be my second choice if I was in your place. Regardless of what branch you join, however, it’s purely your responsibility to set yourself up for civilian life after the military. Regardless of what branch you join there are still programs to further your education while you’re in to set you up for life after the military. Just stay motivated!

The opportunities and skills learned in the Air Force translated well to civilian employment following military service.

I have more of a question than an answer here. Why do you want an MBA? Seems like an intermediate step to an end state rather than the end state itself. As both an MBA and hiring manager, I can say that the degree carries positive and negative qualities in the job market. MBAs are general managers by education, which is also a skill you’ll learn as an NCO or Officer in ANY military service or billet. One of the biggest mistakes I see Veterans making is to go be a manager in the service, come back and learn about manangent, then apply for management roles only to learn that your lack of specific industry or organizational knowledge inhibits your ability to manage (or even be hired) in that arena.

A better question might be ‘what do you want to be when you grow up,’ which I will be the first to admit is one I still don’t know the answer to. But if you want to be in cyber, or medical, or LE, you can probably find a military career that prepares you for THAT transition. Then, if it still makes sense, you could go back and get an MBA to enhance the technical skills that the military gave you. Better yet, you can go get a targeted masters degree in that field rather than spending time learning the civilian version of leadership and management lessons that you already know from your time in the military.

Considering your career choice is all about leading and decision-making, the obvious answer, to me anyways, is to become a Commissioned Officer. You get put onto a staff team and assigned to the position of platoon leader, which usually consists of about 40 soldiers.

However, considering you're a junior, I think you've missed your chance at ROTC, which is one of the few ways to become an officer in the Army. However, you should still contact the ROTC department if your school has one, just to confirm.

Below is an article explaining the other ways:
https://www.todaysmilitary.com/joining/becoming-a-military-officer

Matthew Douglas Below is information regarding the branches. I would look at all the branches and what opportunities that each will provide you. What are your long range goals? Are you planning on working on your MBA while serving? All of the branches offer skills that translate well to business.

https://www.military.com/join-armed-forces/military-service-branches-compared.html

https://www.usmilitary.com/30697/choosing-which-branch-to-join/