I can't speak for the Navy, but the Marine Corps uses the Barron's rating of each college as a determining factor for selection. I think what this means is that, GPAs being equal, the guy who graduated from Harvard will probably be selected before the guy from University of Phoenix Online.
That being said, I was told by the Navy Senior Chief from NRD Richmond who administered my ASTB that he had never heard of anyone getting selected for Navy OCS with a degree from Saint Leo University (where I graduated from the continuing education program with honors

). He told me I should have gone with a technical major from a well known University (ERAU was mentioned).
I was a little worried about that when I applied for Marine Corps OCS, but my OSO told me that my school is rated "Competitive" by Barron's, and schools like Old Dominion, Virginia Wesleyan, and Christopher Newport University are in the same category.
If you are taking classes on active duty, you are probably going to have to attend a non-traditional scool. I think the board members take that into consideration while selecting applicants, so being active duty probably helps a lot. If you were an 18 year old high school grad taking classes online, you might be less likely to be selected for OCS than if you were an active duty Sailor or Marine trying to squeeze a few classes in here and there between dets.
Cheers/ Paul