I pretty much use Bittrex all the time. Once upon a time I had a Poloniex account, but it was suspended because Poloniex stopped being available to people resident in the state of Washington, due to regulations.

So I can't really say that I have enough information to "recommend" (or not) Poloniex... but it seems like they have extensively had issues with their Steem/SBD gateway over the past year, if other people's posts are anything to go by.

=^..^=