Hey Flignats, welcome to the forums! Glad to have you aboard.
Worldwinner has a lot of games similar to King.com's on its platform, and there's a lot more potential to win big bucks there...so definitely check it out and see if it's to your liking. Worldwinner is much, much bigger than all of the sites you had mentioned -- it's on the same level as King.
I suggest you wait for Dukebox's "official public release", when there will be a ton more players active on the site along with a few new cool games. Dukesbox has a ton of potential and the admin team is working their butts off to ensure a positive playing experience.
Yeah, I don't care what the folks over at forumvme say anymore...uVme is dead. With King and Worldwinner both releasing top notch games that have components similar to uVme's #1 game (Fruit Frenzy), uVme has received a stake in its heart.
Anyway, welcome to the forums and feel free to ask questions about any of the games! We've got enough players here to cover most of the games on both King.com and Worldwinner.
Jacob, aka Meikyousisui on King.com & Worldwinner.com