Dracule Mihawk is the strongest swordsman in the world superior to Shanks who managed to stop an attack from Akainu and equal to Whitebeard, the former has the highest offensive power of all devil fruits and the latter has the strongest paramecia, surpassing both the Shiki's Fuwa Fuwa no Mi
the scaling chain would look like this:
Dracule > Shanks = Akainu > Whitebeard > Shiki = 1,497 Exatons
with a scale chain like this I venture to believe that Dracule must have between 2 and 3 Extatons
Luffy, his base is able to hurt Zoan Kaido, his Gears match Hybrid Kaido, his strongest attacks severely damage Kaido and his Bajrang Gun is about 4 times stronger than his Base, Kaido is stated to be able to stop Blackbeard who has the power of Gura Gura no MI, his Zoan Form is superior to his Base, and his Hybrid Form surpasses his Zoan Form
the scaling chain looks like this:
Luffy Base => Zoan Kaido > Kaido Base >= Blackbeard > Shiki = 1,497 Exatons
Gears Luffy = Hybrid Kaido > Zoan Kaido > Base Kaido >= Blackbeard > Shiki = 1,497 Exatons
Strongest Attacks > Hybrid Kaido > Zoan Kaido > Base Kaido >= Blackbeard > Shiki = 1,497 Exatons
Bajrang Gun > 5,988 Extatons
With these scaling chains, I'd venture to believe that if or if Base Luffy should get past 2 Exatons, his Gears should be close to or slightly above 3 Exatons, his strongest attacks should be way over 3 Exatons probably getting closer to 4 Exatons and Bajrang. Gun must be between 6 and 8 Exatons
Considering Luffy's vast array of abilities and Luffy's clear superiority in terms of sheer power, I give Luffy the win.