That's a weird comparison bro why would Gin be considered among the strongest captains in the TYBW when he's 6 feet under.

But if he lived and was in the TYBW he'd be among the strongest captains still, his Zanpakuto is OP and his reiatsu has to be on the higher end if not top of the captains, since Aizen said fights are a battle between reiatsu and he was one of the few people who actually damaged transcendent Aizen. Soi Fon was unable to use her Shikai on Aizen when he wasnt fused with the Hogyoku because his reiatsu was so far above hers but then Gin almost manages to deal a fatal blow to Aizen who was fused with the Hogyoku and had evolved multiple times so his reiatsu at that point was far beyond what Soi Fon fought.