1. They Both have the Same dream to find the One Piece and become Pirate King.
2. Both Have Come face to face with 2 Emperors of The New World.
3. Captain Kid Clashed With Shanks & Kaido
"Strawhat" Luffy Clashed with Big Mom & Kaido
4. Both are wielders of all 3 types of Haki including the rare Conquerors Haki.
5. Both have clashed and Defeated a Sweet General of the Big Mom Pirates.
6. They both have 1st Mates worthy of a Worst Generation title.
7. They both Have Pirate Fleets: Luffy has The "Strawhat Grand Fleet. Eustass Kid also has More than 2 ships which implicates that he has a small fleet as well.
8. They Both were able to resist being mentally & Physically Broken in the Udon Mines.
I don't agree with all the points Kid didn't defeat a Big Mom commander he just hurt him which is different from defeating. In addition Luffy did not defeat a commander but 2 where there was a second emperor Luffy had a connection to all the Emperors but not Kid Whitebeard: Marine Ford and link with Ace Whitebeard make us understand that it is Luffy that Roger is waiting for Blackbeard: Rival dj hero and antagonist at the same time Shanks: Luffy's model Big Mom = Link with Lola from Triller Back, Sanji, Erbaf etc ... Kaido: For Luffy to open Wano to the world and carry Oden's will I half agree with the fleets, Kid has mini fleets but Luffy since the beginning of the manga has literally allied countries linked to him like Dressrosa, Alabasta, the island of fishmen, the island of Hancock, and 7 captains under his orders including a former supernova (Cavendish) She is the difference between Luffy and Kid