We know that Bittrex and Poloniex are the most sought after exchangers.
But I want to know which one is best to trade? and I want to know why.
Thanks.

I think bittrex is the best exchanger that we can use if we will do trading. Most of the whales in the trading world are using bittrex. Bittrex also has better security than other exchanger. I can considered that bittrex is better to use than poloniex.