But it's good to read it again: W. Thomas Smith, "Dispelling Myths About American Soldiers."
Two points should be added. One, Smith, a former Marine, is naturally a bit biased toward the Marines. That's how those guys operate; it's one of the reasons the Corps has such a great reputation. Heck, former Army artilleryman Harry Truman once wrote, "For your information the Marine Corps is the Navy's police force and as long as I am President that is what it will remain. They have a propaganda machine that is almost equal to Stalin's." (Read the correspondence on the page that I linked, it is hysterical.)
Two, Army recruiting numbers have been helped by raising the maximum age for new recruits. This was done mostly to get folks with specialized skill sets, but it should be mentioned.