Simple and easy...
Sanji's result after training was (decent observation + armament not good enough)
Zoro's result after training was (decent armament + observation not good enough)
Luffy's result was the MOST BALANCED out of all monster trio... with decent armament, decent observation, decent king's haki.... you can add even DF training on top + the fact Rayleigh conveyed to him the knowledge of the advanced versions of both of observation and armament if he came to face such opponents, which he did with Katakuri and now Kaido... he can aim to master them
So... the answer is clear as crystal... but you are free to just stay bias for Zoro just for the sake of being on Zoro's side by using the same god damn reason every time (well we didn't see Zoro's full power yet)
But we both know he sucks at observation... and he is not advanced in level of armament like luffy now.. and he didn't show king's haki... no DF also
So... again... I don't know why people even try to argue.. but whatever...
Let's start with CoO...
All 3 have Observation haki and there is no difference in level mid-combat to the point that it's basically useless...
You cant tell the difference between their CoO to say someone had decent while the other has not good enough.
Next is CoC which does absolutely nothing except knocking the irrelevant fodder out.
So, we have the useless CoC and CoO which levels cant be told apart in combat out of the window.
And we get to the Haki that matters the most - CoA which is where Zoro is miles ahead, since Alabasta while Luffy's CoA failed against CoA-less Hody Jones...
So, Rayleigh taught Luffy the basics of CoC which is useless, CoO which you cant tell apart and CoA which is broken by Foddery Jones.
So, that's what makes Rayleigh a better teacher and Luffy's TS results better?
Rayleigh couldnt teach Luffy how to be a better Rubber-man, he had to do that on his own.
While Zoro was taught how to be better swordsman by the best swordsman through fighting the best swordsman and gaining experience against an actual top tier while Luffy was improving against animals which we cant even call a high tier...
How can you possibly place Luffy's training above Zoro's? It baffles me...