Saying seraphim are better than King's mean.
S-hawk>Mihawk
S-Shark>Jimbei
S-Bear>Kuma
S-Boa>Hancock
Momo>Kaido.
Just because they share theie fighting style or power.
But WE all know it aren't the case the original Warlord Can beat the seraphim if they exploid their weakness with Mihawk literaly curshing all with a pocket skife.
Why? Because the warlord and King have powerfull haki which is>>>>DF and most other ability.
Beating S-Shark will atmost give Sanji thé benefit of doubt to damagz King a bit but he still need some legit feat against top tier to have a chance at beating King.
The way I see it Sanji will Surpass King in the next Big Arc for now he IS still weaker.