Bittrex for me but i should also try other ones. More options will emerge as decentralized exchanges come into play.
I'll go with bittrex too but their new regulation about enhance account verification is giving me some time to be lazier.
i highly recommend YOBIT.Net .thats what i use for trading try to check it out and check the difference from those that you use too exchange
I don't recommend yobit for using it to those altcoins that are useless, they are giving everyone stuck withdrawals. I used them with bitcoin and ethereum, no problems with these coins.