As a Wharton undergrad alumni (who's successfully pissed away his degree) who got his MSBA (the S is to distinguish it from the resident school) from the Boston University distance education program, I'll throw in my two cents.
Career goals and timing will throw some curves into your calculations. One, realize that the Marine Corps doesn't give two shits about officers getting graduate degrees. Other services tend to give it more credit. As they say, the three things a Marine promotion board doesn't care about are "medals, muscles, and master's."
A guy getting out after his first hitch at 30-ish years old is in a good position to get accepted to, and attend a top resident MBA program, especially if he is single or has a wife with decent earning potential. He has to think about what he wants to do, though. Different schools are better known in different fields. For example, University of Chicago and University of Pennsylvania (Wharton) are known for finance and a strong quantitative emphasis. If you want to build your own business, you may not need or want an MBA to sell shit on E-Bay, but if you are going to try to build a business requiring venture capital, you could do worse than to go to Wharton and have some of the country's top entrepreneurs coaching you on building your business plan.
For the guy getting out at 20, it's probably not so much of an option to spend a couple years in residence to get an MBA. However, a degree from one of the "everywhere else" schools is certainly not going to hurt. It shows that you know more than just how to fly a plane and will put you ahead of the thousand other ex-military around. A friend of mine who worked closely with a major defense contractor in an acquisitions billet told me that former COs would call his civilian counterparts regarding positions. The conversations would go along the lines of,"So, what experience do you have in defense contracting?"
"Well, I was a squadron CO."
"We don't have squadron COs at XXX. What else did you do?"
Yes, the military experience goes very far in getting one in the door ahead of some other guys, but the more of the total package you can give, the better chance you have of getting hired.
The alumni networking of distance or online programs is much less than in resident programs. However, in a distance (extension campus), type program, you will get very close with your classmates, and those are some of the people who later will get your resume put closer to the top of a pile. Also, whether online or at an extension program, go to one that has a reputable brick-and-mortar campus. You will get access to alumni directories and career placement/referral services, just as if you went to the main campus. Those don't hurt.