Poloniex always adds coins later in the game. A lot of coins get instadumped as soon as they get added in Poloniex because people did their buying in other exchanges that added the coins earlier. Bittrex I think it's one of the best exchanges to get coins faster than most people, they definitely add coins before Poloniex does. Of Course Poloniex got the best volume out there, maybe yobit can challenge it but im too lazy to learn how to use yobit and chinese exchanges in general.