I think Bitcoin trading in Poloniex can be the best exchange option because this site is complete and has many features for trading use.
What is traded not just Bitcoin. Coin offered him a lot.
Active members are many each day, always more than 5000 active members. Trading in poloniex is quite simple and powerful because it comes with trading features such as bolinger band, FIBO, SMA and MA that help analyze where the next price movements. Although sometimes the analysis is sometimes wrong prediction.
Bitcoinnya volume is much in its 24 hours is about 20000 btc not included with other coins such as ETH, XMR, USDT. Poloniex also features stop limit order which is useful to minimize possible losses incurred during bitcoin trading. Not only used for trading alone can also exchange or exchange bitcoin with other coins such as ETH, LTC, XMR and so on.