Marines do have the most intensive basic training of all the armed forces. I have family/friends in all branches except the coast guard, and they all sit around and compare notes on the services when together. Let me just say that my cousin in the marines was laughing at how easy my wife's basic training was (air national guard.) His was almost twice as long and twice as hard. So yeah, they may carry a bit superiority in their attitude, but if you've ever seen one of those gaunt, fearsome men with the fire in their eyes at their basic training graduation, you know they've earned it.