If you trade using these, instead of on an exchange, you pay a flat, roughly 10 cent fee (2c for subscriber) per trade, instead of 0.2% of the total. (Assuming BTS = .5 cent).
For subscribers, you will pay lower fees using BTS if your trade is at least $10 of value.
For non subscribers you will pay lower fees using BTS if your trade is at least $50 of value.
And your fees burn BTS and thus help support Bitshares instead of going to a centralized exchange.
As long as we can get some liquidity and you arent dealing with issues of a big spread, this is clearly superior.