I have also played both, and Rugby at quite high levels, (I was scouted to play in New Zealand, and played in front of Canada scouts) and I would have to say they are different sports and are not as easy to compare as you think. Football is dangerous because of the pads, if you tackle like that in Rugby you will get hurt severely, but that doesnt remove the nice hard helmet smacking you in a soft spot, that shit hurts and you get more trauma injuries from the higher impact.
That being said try and compare a football hit to a solid dump tackle in rugby and you will see the difference, imagine my lifting you onto my shoulder 5 feet in the air minimum and jumping off my feet slamming you onto your back and head while landing my shoulder into your stomach. (doesnt happen that often though)
There are lots of big hit videos out there, but the advantage of this one is that they are all legal hits.
RIP-my ACL, MCL, Meniscus, and tendon in neck...oh and my season, job, trip to New Zealand...etc
To have a great adventure and survive requires good judgment. Good judgment comes from experience. And experience, of course, is the result of poor judgment