I feel like ORAS really asserted that battles aren't everything, that contests are just as important. Lisia is the character who represents that, since she's not much of a battler. So Lisia is basically the "Pokemon Champion of Contests," the same way that Wallace, her uncle, is the Pokemon League Champion in Emerald. I liked the connection, but I really wished that Lisia would be a part of the actual storyline somehow. She's only involved in contests, so she's kind of a noncanonical character.
She's ok I guess, but Chaz is a little narcissistic, don't you think?
I liked Chaz, though. His narcissistic personality made the contests more competitive and made me want to beat him badly. I guess it's just fun to put down people who like to put down other people.