If you have seen both fight you would have to be around 50 at least likely a bit older to have seen an Ali from the 60's.
with that said if you are younger than that you have to rely on video wich is ok, however, it is also important to have seen their apponents fight other heavyweights to gauge their ability.
For example; watch Frazier fight Quarry twice or Norton fight Quarry or Petterson fight Chuvalo. then perhaps watch Bruno fight Lewis etc...
A real fan of the sport knows that a young Ali at 6' 3'' and 215 would be able to box Tyson for 15 rounds, I can not imagine Tyson being bigger and stronger than Sonny Liston or have more determination and toughness than Joe Frazier, or shear power than George Foreman.
Could Tyson beat any of them??
So bottom line: Ali rather easy.