Chelsea's style doesn't fit him too well. He's more playful and attacking minded, and Chelsea defends a bit more ruggedly. He isn't always as solid, but if you'd imagine him in a more attacking team like Manchester City next to Kompany, I think it makes a lot of sense. In a more playful, attacking team where you can change positions and where you can rely on your midfield, I think Luiz could be world class. Italian style football especially, cause Man CIty's style looks more Italian than English to me.
I don't know about Barca, cause if you pay 30 mil, logically you put him in your starting line-up. Are they planning on a Piqué-Luiz central defense partnership? I don't know about that, I'd rather see him go to City for the sake of football.