Joker's not just crazy and dangerous, but he's an evil genius(imo on par with Lex Luthor)! Joker's ability to predict opponents actions and reactions well in advance gives him and his gadgets the big edge. Also master of chemical weapons!
The Joker is over six feet tall, incredibly fast and strong, and a skilled hand-to-hand and melee fighter. In addition, he is adept with a wide variety of ranged weapons, from pistols to rocket launchers. His insanity hides an genius intellect, and he has proven to be a master chemist, as well a brilliant strategist. Vaas Montenegro is 5'10, a drug addict, and has been proven to be only barely competent. The Joker wins this, hands down.
The Joker, any variant of the Joker would shred vaas. Vaas couldn't kill a suburban white boy with no military training. Joker destroys the bat family and makes batman break his only rule. Joker wins /thread
Vaas was all talk and acted only when he was sure he had the upper hand. Joker would destroy Vaas in any number of ways, and his creepy sister too.