I've done both. Even in fundamental research, you have to "do" something in order to make an idea worth considering. Halley didn't just jot down that a comet might appear in 1758 [0]. He didn't just suggest that a comet could be used to test Newtonian mechanics. He had to work his computation from start to finish, find and fix the bugs, show convincingly how his result actually followed from the theory, etc. And computation was hard back then. Maybe 1758 wasn't the first answer he got.
Likewise other theoretical and fundamental work. Note that this is aside from the question of who gets "credit." Fortune tellers take credit for predictions. This is about what it takes to do good work under most circumstances.
