There is a difference. Although I'm not any kind of an expert on Bitshares, as I understand it, witnesses in Bitshares get to set their own pay and this has led to a race to the bottom with most witnesses receiving only 10% of the scheduled pay. This system of variable pay was considered and rejected for Steem to ensure that witnesses have ample resources necessary to support the platform. It is up to the community to make sure that witnesses do a good job and vote out those who don't.