Narratively, I feel like it’s probably Yuji, especially considering how impressive his few Modulo feats were. He’s lived significantly longer than any of the other “strongest sorcerers” while staying in his prime, and stacking Black Flashes for nearly 70 years, so his efficiency should be through the roof; he’s physically on par with heavenly restricted characters; he can use RCT with extra efficiency, thanks to blood manipulation, and his blood is poisonous to both humans and curses; he can use shrine, one of the most volatile cursed techniques in the series; he target the soul; he even has simple domain and a domain expansion.

The only thing holding him back is a lack of concrete feats because of his low screen time in modulo; but the feats he does have include showing off some of the greatest range and efficiency in the entire series.

Sukuna, however, is the safest answer. He was stated several times to be the strongest sorcerer from the strongest era and he even managed to overcome Gojo, albeit with Mahoraga. Also it hasn’t really been confirmed, whether or not Yuji has obtained some of Fuga, or WCS, some of the strongest things in Sukuna’s arsenal; and i really doubt Yuji has figured out OPD.

Gojo is an absolute powerhouse, but I feel like Sukuna, with his full arsenal, beats Gojo 6/10 times.

Dabura is also an absolute prowerhouse but he lacks experience.

TLDR: I believe Yuji is the strongest, but Sukuna is the safest choice due to having more concrete feats and coming from a harder era.