I've been using Binance with success. Very slow though as they are on the other side of the world which creates a delay. I have had money vanish from Bittrex not because the account was compromised, but Bittrex lost the records. I also don't think they have a customer support team. I don't have any evidence that they have any staffing to deal with support issues. I haven't tried Poloniex or Changelly.