This depends completely on the equation in question. For instance, both are strong bases, so if that’s all you’re worried about, yeah, they’re about equivalent. But potassium tert-butoxide is way bulkier than potassium hydroxide, so if sterics are a concern (e.g. in nucleophilic substitution and elimination reactions) then there’s a huge difference. Also, the hydrogen bond in KOH will matter in some reactions, not in others. Those are the big differences that jump out to me, but there may be others.