Shanti has been diagnosed to have brain tumor. You would prefer to give her betamethasone/dexamethasonc over hydrocoisonc as steroids to decrease her cerebral edema because:

(Ref: KDT 6/e p285) Triamcinolone, betamethasone, dexamethasone and paramethasone are selective glucocoicoids (have zero mineralocoicoid action). These are preferred for cerebral edema because they lack salt and water retaining potential (mineralocoicoid action).