Vegeta can be Bulma's husband, partly because Vegeta is very strong. Vegeta is second only to the Monkey King in strength, and he can become a super Saiyan. Leping is just a local tyrant, and his skill is far from that of Vegeta. Bulma likes strong men, so strong Vegeta is more to Bulma's taste.
Vegeta is an indomitable fighter, and he is eager to defeat his arch-rival the Monkey King in the future. In order to defeat Wukong, Vegeta practiced in the gym and gravity room day after day. At the beginning of "Artificial Man", Leping thought that he could not keep up with the Monkey King's practice progress, so he was not obsessed with practice like Vegeta. Bulma prefers hardworking Vegeta to sloppy Leping.
Vegeta will stick to anything until it is realized. It can be said that Vegeta is a little paranoid. When Vegeta decided that the Monkey King was his opponent, he vowed to defeat Wukong. Vegeta decided that Bulma was his wife, so he only looked at Bulma and ignored other women. On the other hand, Leping is not as devoted as Vegeta. Birds of a feather flock together. Bulma, who is also paranoid about science, prefers Vegeta's paranoia.