Really hard to say as Robinson was only stopped once in his career due to exhaustion and Ali managed to outlast Joe Frazier in Manilla in a fight where both men were dishing out tremendous punishment and absorbing it too. Ali also survived a near knockdown and knockout in his first fight with Frazier before having to get up from that 15th round knockdown. Robinson had great fights with Turpin, Fullmer, Basilio, LaMotta and Olson and Ali survived tough battles with Foreman, Bonavena, Shavers, and Norton. Both men certainly knew how to pour it on and comeback from possible defeat if need be but I got to give this one to Ali by a slim,margin.
Ali because he was what I call an all-weather fighter. He can fight in any weather and clime and that he amply proved when at an already advancing age, he fought and beat George Foreman in the desert-heat of Kinsasha, Zaire in 1974, Joe Bugner and Joe Frazier in the humidity of Kuala Lumpur and Manila in 1975, respectively.
Robinson quit due to heat exhaustion in a failed attempt to win the light heavyweight title from Joey Maxim in his prime.
Ali easily. He had 15 round fights that match Hagler vs Hearns for intensity.
winning or losing both of these men always managed to pull out a second wind in the closing rounds and close the show.great example's of this are Ali vs Bonevena/lyle/frazier III and Robinson vs Lamotta(valentines day massacre) or Robinson's 1 round left scenario in his second fight with Turpin
