I use Bittrex the most and I quite like them but you're right that the charts on Poloniex are better. I don't understand why Bittrex doesn't have trade volume on the chart. It's just as important as the candles imho. Also Poloniex stop limit orders are much easier to use.
Tried Cryptopia during the recent Chaincoin pump and it was great except for quite a bit of lag and also the volumes are very low on all but a handful of coins.