The responsibilities are likely much the same. Custom, tradition and professional staffing philosophies account for the variance.
Another factor is that the number of each officers at each rank is controlled by law. The Navy has chosen to use a one-star billet elsewhere, and use an O-6 billet at USNA.
A Navy O-6, post-major command (command in their warfare specialty at the rank of Captain), is considered to be at the top of their game, in play for flag officer consideration. All Commandants in recent years are post-major command. The Commandant is not an official command role, but head of a department within the entire USNA complex, reporting to the Superintendent, who is in the command role. Of course, the role of the Commandant is the pre-eminent one amongst the captains and colonels in the USNA family, with special powers to adjudicate offenses and take certain actions.
For many years, the USNA Superintendent was a 1-2 star. Some troubles occurred, some swaps were made, and the USNA billet became a 3-star and some other command went from 3 to 1 or 2 star leadership. Similarly, for many years, at the Pentagon, the Director, Army Staff and the Director, Air Force Staff, have been 3-star billets. The Director, Navy Staff, was a 1-star until 2001, when a 3-star was brought in. Again, swaps were made.
Culturally, a good example of differences - not who’s right or wrong - between Sevices is when I was a BattO at USNA. I was the Officer Rep for Navy women’s basketball, handling good order and discipline on the road, working with the team captain, the team academic adviser and the coaching staff, putting in several hours a week, even out of season, and traveling to every game, and attending most practices. This was in addition to time-intensive BattO duties, teaching Ethics class to 3/c mids as an adjunct prof, and O-rep for 3 other groups. This was the busiest shore duty I’d ever been assigned, with a lively OPTEMPO. At my first game at Army West Point, I went in search of my counterpart officer rep, as a courtesy, before the game. To my surprise, I met a colonel, a captain (0-3) and a senior enlisted leader, all of whom were sharing the duty. Again, not right or wrong, just different.
