Both talk a lot.Luffy is a serious person whenever he walks across you but his dream is still to become the pirate king and he do all for this. If someone leaves the crew he's serious and do all to get him back, sometimes he get angry. Zoro is a mad, sadistic, cold and angry person all the time. He would do all for Luffy and sometimes he go too far but he dont care about this. Zoro often fight with Sanji and don't like him either. Zoro is the right hand of Luffy and want respect for that.