Football is more of a physical chess match. We had to learn hundreds of plays and variations and make pre-snap calls as well as mid-play rotations. Rugby required much less thinking but more reaction. Because you can't block or be in front if the ball you have to be aware of the field at all times because one or two wrong passes and you go from offense to defense and must completely change your position and play style.
Have played both and that's about right. Rugby's got that unplanned constant action and frenzy that's also typical of earlier sports like soccer. Football's more strategic and measured, especially the US pro version. Rugby equipment or lackthereof relative to football is essentially something like early football with leather helmets before all the enhancements in protection.
The heavier guys still have to be in somewhat better shape and lighter to play rugby because of the constant flow. There's still room for some preplanned plays, for example plays off the scrum which is like the line of scrimmage.
As far as injuries, you're going to get more bones broken in football given the heavier weights including additional weight of the equipment and greater bursts of speed over shorter periods of time. More gashes, cuts and gouging in a more primal sport like Rugby that hasn't got a lot of protection.
Lots of similarities tho, as you'd expect since football evolved from from Rugby and Soccer in Canada and the US. Japan also plays college football.
