Yes always trade in the internal market as per voltagrou when converting SBD to Steem. Right now you will get less Steem per SBD than 1 month ago, because the SBD token will get you about $1 US worth of Steem and SBD price has gone up significantly. Some like https://steemit.com/@flauwy are considering holding SBD as he explains in his latest post. I hope this helps, greetings!