I personally like huobi, binance and bifinex. These are reputable trading floors and have high exchange rates. But the use of huobi on mobile apps makes it easier for me to operate and build plans or more flexible.
I don't want to spend more time looking for a good exchange, because they are all different so better go for the great and huge one. I trade with Binance and the experience is really good so I stay with this for good. But if you have your bounty token, you have no choice but to open an account on which your coin is being listed.