Bittrex is the most expensive exchange in terms of commission, but it is the most popular. It is necessary to look not only at the commission, but on how reliable the exchange is, how many pairs there are traded, can it be earned on it?
This is the main thing I do always see on how an exchange is reliable not necessarily on seeing on its fees when you do decide to trade on that one but yet there are really people that they do really serious when It comes to fees while they are trading or exchanging up.I haven't see any free comparison,i don't know if it has being listed by other members but so far I haven't seen that one yet and its better to make your own since comparing them would be somehow simple.