Warren for definites, if u can get Gary Lockett and Michael Jennings big fights in america against pound for pound ranked fighters, You've gotta be doing something right. Blindsiding GoldenBoy by stealing the Kotelnik fight from Victor Ortiz fight for Khan is another stroke of genius! Say what u like about his fraudulent matchmaking and bitterness against anybody who doesnt join his party etc but he does manage to build great records for poor fighters, before getting them a massive payday. Plus he straight up ended Mickey Duffs career worse than Pacquiao did Hattons.
Duff was brilliant in the 60s, 70s and 80s; Warren 90s and 00s. I give the edge to Frank because (believe it or not) he had to compete against must stiffer competition; Duff (Astaire and Levine) had it easy, with his/their monopoly and because of the lack of Internet, less aware fancy.