Sanji AP: Country level, higher with DJ, even higher with IJ 2 AP amps.
For speed he has this: FTL, higher with DJ, far higher with enhanced speed, even higher with IJ
Durability Sanji: Resistance to Electricity so BM's Attacks with Hera will prolly not have any effect on Sanji? Shattered Queen's sword, higher with Buso Haki
Stamina: Superhuman. Pretty good ones in Wano like taking King's beak and getting up unscathed, fighting King & Queen at the same time even tho getting overwhelmed. And using that enhanced super speed in the end to end the fight but thats not enough tbh or close to BM's stamina
Range: Standard Melee range with kicks, at least 10 of meters (potentially hundreds of meters) with his flames
Intelligence: Hes for sure smarter than Big Mom in combat
Buso Haki: Intermediate Stage
Observation: Bruh
i think its common sense that Sanji far exceeds BM in that department
So Sanji's advantages here are only Speed, Intelligence, Observation Haki thats enough for a mid diff ngl when hes far faster than BM and could potentially harm Big Mom with Dura Neg attacks (with morals off ofc)
Big Mom has for AP: Country level, higher with Homies, far higher with all homies, even higher with Soul Amped Form so 3 AP amps. She slams Sanji on that department ok
Speed: FTL, higher with homies 1 Speed amp
she wont be able to catch Sanji for a while. Sanji probably can damage Big Mom with Diable Jambe since its Dura Neg.
Durability: Fought Kaido for at least a day and sustained minor damage, completely unharmed by Brachio Bomber (that attack would kill Sanji ngl), far higher with Soul Amp, withstood several attacks by Kidd and Law requiring them BFR to take her out of the island to defeat her. Survived being in the middle of the explosion of the bombs that could destroy Onigashima.
Stamina: Fought Kaidou for at least a day. This is as much as Luffy fought Kaidou btw which the fight seemed way longer ofc. Took 3 Dura Neg attacks by Law that targeted her organs as well as Kidd's attacks that either broke her bones or made her bleed, and was still implied that she would have won if Law and Kidd didn't BFR her.
Range: At least tens of Kilometers with sword swings that have sliced across Whole Cake with her homies being able to create massive storms instantly.
Intelligence: Not that good in combat, overconfident sometimes ngl
Intermediate Buso possibly Advanced since she could apply Emission in the attack to Page One since it didnt make contact too. So superior to Sanji's Buso
Observation: Only Important Observation feat she has is sensing Enma
which is sensory
Hao Infusion: Yeah she destroys Sanji pretty badly with this ngl its another AP Amp which makes it 4 AP amps for Big Mom.
BM Advantages: Superior AP, Durability, Stamina, Range, Buso, Hao Infusion
Well actually with the AOE advantage she has and the Flight too she actually low diffs not mid diff now that i analysed this fight better.