I'm gonna say Frazier. He was better at slipping on the way in. Joe fought faster, sharper boxers. Jimmy Ellis, Jerry Quarry, Buster Mathis and ofcourse Ali. Dempsey? The sharpest guy he faced was Tunney and he got peppered.
Dempsey was past it for Tunney, he had no trouble beating Gibbons,considered a clever boxer. When I saw this thread I though the answers would be 50/50 for both men.
Dempsey was coming off of a 3 year layoff, and was 3 years past his best before it. That's like insulting Frazier for losing Manilla Dempsey fought great, sharp fighters in Gibbons and Fulton
Both are under rated as swarmers wit some defense for sure ... Tyson may have been the best heavyweight defensive swarmer ..
He had the best defense for a guy his size but its a little iffy calling tyson a swarmer. His inside fighting ironically wasn't that great, he was easy to clinch, and he wasnt a volume puncher.
Tyson wasn't a swarmer though and I'm not sure his defense was better. He was vunerable against great inside fighters and he couldn't fight in clinches at all. Great outside defense though.
In terms of generally being difficult to hit clean I'd say Dempsey: his bob and weave IMO was less rhythmic and thus less predictable than Frazier's. On the other hand, Frazier was maybe a bit sharper in actively reacting to and evading some shots. Those reflexes he showed during FOTC were Jedi-like.
Fraziers movement was erratic on purpose, Futch said they worked that with Frazier before there first clash so Ali couldn`t time him with the jab.
Dempsey was better defensively because, in addition to bobbing and weaving, Jack had much better footwork than Joe.