Both these guys are in my all-time Top 5 pound for pound list.
They both were Great boxers, had Great footwork, Great defensive skills, they both threw Great Combination punches, they both were the BEST of their weight Class for years.
Pep did come back after 6 years, BUT only 1 boxer that he beat had a winning record, so I wouldn't count that. He did come back after he had suffered serious injuries in a plane crash and that says something.
When Robinson came back after 2-1/2 years he went on to win the Middleweight Title several times.
The only loss he had in his 1st 131 bouts was against LaMotta and Jake out weighed him by 16 pounds. Robinson's record was 128-1-2 before his 2nd loss.
The only loss Pep had in his 1st 136 bouts was against Sammy Angott in 1943. Angott was the Lightweight Champion at the time and out weighed Pep by 4 pounds. Pep's record was 134-1-1 before his 2nd loss.
Robinson fought Angott 3 times and won all 3 times, and Robinson weighed the same as Angott in their 1st match and the scoring was Kutcher scored the fight 6-3-1, Lacky and Loughran 7-2-1 in that bout.
Robinson did beat Pep when they were Amateurs BUT Robinson was older and Heavier then Pep.
The only thing that I see that would separate these two Great Boxers is Robinson's punching Power and that's why I will have to go with him.
When Robinson was a Welterweight, he was the BEST EVER!