But you can discard any time. Why are you prefer Fusion Sage? And it can be fusion-sub, and spell is more likely to be negated than hand monster. Sorry to ask but I really don't understand.
Monster effect on hand is rarely to be negated at least for the cards right now. Most of them negated when destroyed only. On the other hand, spell is negated by most things: jammer, cv, drain and etc. More over swamps can be fusion material.