Luffy got 1.5 billion for tons of stuff like the assassination attempt, beating Cracker, beating Katakuri and escaping safely.
Zoro got 1.1 billion for beating King and I suppose being under Luffy but it doesn't say anything about the quality of their opponents.
I enjoyed both King and Katakuri and even strength-wise, they were both incredibly powerful and intimidating, they simply specialised in different things. I don't see the point in using bounty to try and hype one over the other. Kata had +1 billion and was seen as invincible, King had 1.39 billion and was Kaido's right-hand man. They were both fine.