1. Luffy's foot speed > Sanji'sWhat speed feats do Luffy have that prove he is faster than Sanji (who fights solely through his legs, this directly correlates to speed)
Maybe the fact he can run through the air? Running 5000m under sea level (on par with or surpassing merfolk)
2. Luffy's striking speed> Sanju's
3. Luffy's strength > Sanji's
4. Sanji's kicking technique is better than Luffy's, like you stated he trains and fights with his legs.
5. Better technique doesn't necessarily mean more power
6. You constantly talk about this ability to run at high speed in the high pressure, a feat that Luffy's cannot even attempt to do, not because he is slower or less durable in comparison to Sanji, but Luffy and all other DF users cannot control themselves properly if at all when underwater.