As mentioned before, Rugby is a more flowing game. The current South african team is plagued by political crap and is not as good as it should be. Their ball handling sucks.
american Football is a tough game, make no mistake. I tried to get into it while in highschool, but failed the physical - too many "problems" with knees, back, hearing, too many joint problems. The doc just asked "What the hell have you been up to the past 16 years?" - reply? Rugby!
I can say that Rugby ruins every Winter for me!
I played support (Not sure about the English name for this position - the Afrikaans name is Stut). Basically in the scrum everytime. A lot of dirty stuff going on in there. I played League for a short while after school but got banned from the local club in SA.
All in All, both are tough games, but AFL has evolved a bit and organizers realized that the helmets and pads are needed to prevent serious casualties.