I haven't used a lot of exchangers but out of the few that I have used I can say that hitbtc i s my favourite in terms of how it works but idex is cheaper in terms of charges on transactions and withdrawal. Just saying from my experience though.
Mine favourite one is Binance. Kucoin is alo very similiar to Binance as these Chinese exchanges are taking over the market. I will prefer idex over etherdelta as etherdelta is not very user friendly.