Note that these other markets are providing liquidity for SD at their own market rates as opposed to Steem's internal system.
The 'Convert to STEEM' button, which as you say takes a week, will convert SD to Steem at the internal market rate at the time of the conversion based on some aggregate price feed of the witnesses.
Perhaps this is a silly question, but does the internal rate better match $1 per SD?
It uses the weighted median of the week between the request and the conversion to calculate the amount of Steem you get. Doesn't help when you sell those at a loss.
Thanks! I was going to edit this post once I found out that it was the median price for the entire week! I'll leave it as is for the sake of readability since all the edits can be seen on the blockchain, but the Steemit UI doesn't show them.