I played rugby and football through highschool and football is a much harder game by a wide margin. Rugby is more akin to soccer and consitent movement and endurance. Football is about speed and toughness. You need all those stops and starts because it's far more explosive and things happen blindingly fast and brutally that just doesn't occur in rugby.
“There is no such thing as a weird human being. It’s just that some people require more understanding than others.” - Tom Robbins