I think if you are talking about the performance i think they are both the same because sometimes the price of altcoin in bittrex are lower than poloniex but sometimes poloniex are lower that bittrex..
In terms of price crash for altcoin both are the same decreases because i think it will be depends in the market and traders if they seen the price is in other trading site they will transfer their funds and sell it there that is why the price will both the same.
I'm a little surprised that one hundred Bittrex exchange is still afloat, internnesno how in the last season, bitcoin could not resist after their hacking, and after all a lot of talk about the fact that the administration refers to this name. .