I have held money on Bittrex, Poloniex and 1Broker with no problem. All three of them take security very seriously, and 1Broker has been around since 2012, never screwed me once.
But considering STEEM/SBD - You can keep them here in Savings if you like, or power them up!
Thanks for the prompt reply and the info. Much appreciated.
Glad to be at service :)