People who say luffy hands down are wrong.
Luffy and zoro are closer to strength.
Luffy zoro and Sanji are considered the big three in terms of strength. In fights luffy takes on the leader of the enemy group while zoro usually goes for either their swords man or their second in command.
Luffy fought mr 0 aka crocodile the head villain, Zoro took on Mr. 1 the guy who can turn his skin into steel and Sanji took on Mr. 2 the 3rd in command.
Earlier in the arc, they run into the organization when Vivi was introduced and they fed and got all the straw hats drunk, all except Zoro and Nami. They just played dumb and pretended to be passed out because they didn’t trust these people for being overly nice to them.
During the night the organization of bounty hunters were meeting in the center of town discussing their plans and were getting ready to turn the straw hats in for money when Zoro shows up.
Zoro took on the entire army of them and killed most of them. I’m not actually sure if they died or not since it is never clear on the show what is knocked out or dead, Zoro does show he doesn’t mind killing people though.
Luffy wakes up and runs across the aftermath of the fight and one of the injured people tells him Zoro attacked them. Luffy gets angry and thinks Zoro just went on a killing spree just for the hell of it and attacked him. Zoro tried explaining himself but Luffy kept attacking eventually Zoro got pissed off and just went in for the kill. The thing is they both went at it with the intention of beating the other they weren’t holding back, Luffy was too stupid and thought Zoro betrayed them and Zoro just got too angry and didn’t care for reasoning anymore.
Naomi eventually got between them and stopped them.
The 2 of them never really face an opponent to compare their strengths other than Arlong and hardy Jones.
While Arlong beat zoro quit easily we have to take in mind Zoro was still healing from his fight with Hawkeye. In fact, Zoro wounds were that bad that Arlong himself was in complete shock when he saw the wounds which says something.
With hardy jones, both Luffy and Zoro beat him very easily.
Zoro fought him underwater while Luffy fought him when he was junked up on all the steroids.
Finally, Zoro and brook are the only members of the group who can do serious damage to Luffy. Luffy is immune to most blunt attacks and electricity because of his rubber body ( the fact he bruises when Nami hits him shouldn’t be possible and is just a gag they do ) Luffy’s biggest weakness besides being under water, sea prism stones and haki would be blades.
So brook and Zoro are the only members who can truly kill Luffy, well there is also Sanji since he learned Haki too.
So my conclusion is Zoro is equal to Luffy, he’ll Zoro might even be stronger slightly because he is the only one who trains daily. Also, take into consideration that Zoro after fighting that vampire villain with Luffy faced off against Kuma. Kuma made a deal with Zoro and spared Luffy. However, Zoro had to take all of the pain and tiredness Luffy had in his body. It was shown only a little bit was extremely painful and Kuma even stated that Zoro should have died.
So add Luffy pain and exhaustion and add that to his own the very fact he was alive after that fight shows his endurance is high.
So again I say they are around the same level and if both went out to fight and not holding back the fight could go either way.