Steem - and steem and SBD are so close it does not make a difference for that purpose - has a 50 times market capitalization then bitUSD. Daily trading volume of steem is 5 times higher then MC of BitUSD.
You can't compare them in regards to peg stability.
I'm not sure what you are talking about. Bit USD and SBD have similar market cap, as do BTS and STEEM.