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I'd say that Sailfish does everything that MBI's firmware does, because Sailfish is based on the MBI code, it adds some very nice new capabilities. MBI's 7.0 firmware acceleration was created in Sailfish, and Sailfish continues to lead the way, with not only acceleration, but the ability to change temperature and speed on the fly, a much nicer bed-leveling routine, and any number of other improvements.
Upgrade, you won't regret it! Whpothomas' guide is quite good.