To both the posters asking about which service, just ask yourself what is most important. Is it serving as an officer in the U.S. military? Is it serving as an officer in a specific branch (Army, Navy, AF)? Is it getting a scholarship? I remember at one visit my daughter went on the ROO asked her, "What does Army ROTC do?" She looked at her Dad and I and the ROO said, "I am asking you, what do we do here?" My daughter didn't look too sure of herself and answered, "you build officers". He about fell off his chair. He said "YES!" And he also told us that very few kids answer that way, they instead usually say that we give scholarships, or teach leadership. Those are partly true, but he said, our purpose is to produce officers. Getting a scholarship is not a good reason to apply, wanting to be an officer is an excellent reason to do it.
As far as the second poster that asked about whether or not he/she should just do Army because of a lower score, it is true that the average ACT/SAT score might be lower with Army, but remember there are a larger amount of scholarships given with Army ,meaning it is still very competitive, they just might go deeper into the pool. And you also have to remember that Army gives a greater number of 3 year Advanced Designee scholarships than 4 years these days. Scholarships are also awarded in all situations on much more than test scores, the whole person is considered. Different algorithms for each service too, in how heavily weighted the GPA test scores are. Like mentioned above, your type of major definitely matters very much in AF and Navy, if you are looking at a non tech major or are not 100 percent sure, then Army and Navy-MO do not care as much about what your major is.
As far as which service, what do you want? Like Pima has pointed out on other threads, if flying fixed wing is the goal, then AF is the answer. I would add to that, if you want to be on a ship, that should also be obvious. If you want to be the "boots on the ground" then Army or Navy-MO. And there are definitely lots of nuances in between. But that gives you the basic "obvious choices". If you don't know exactly what you want to do, but you know you want to serve, then why not apply for more than one and start doing your research so if you get the amazing problem of getting to choose between more than one, then you will have a better idea what to do.
Good luck and keep us posted!