Preparing for the Letters of Rec

Well first hurdle: choosing recommenders.
There are a lot of things to consider here, including how much they like you, the leadership you have displayed in a certain post, how VIP they are and so on. Most important though is that they be EXCITED to help.

Second hurdle: (for you) Make sure your Marine recommenders aren't too tough on you! Remember, recommendations should help you get accepted!

Third hurdle: Content. Here, you can maybe have a chat with your recommenders to "remind" them of stories and idea that they might want to mention in your recommendation.

And that's that. One last note for you: unless the professor is one in a school whose MBA you are applying to, forgot about him. You have probably done MUCH more interesting stuff in the Marines.

The choice of recommenders is always RELATIVE. Meaning we look for those things I wrote above, but we choose recommenders based on what your other options are. So, for example if you still have a second recommender from the Marines, who would give you a great recommendation which shows your leadership and achievements, and gives a different perspective from your first, then yes, it's still better.

So I can't give you an absolute answer without knowing all your possibilities, but you get my drift...
Hopefully this helps,