This seems like the big issue, ultimately. You get Joe who spends his and does splashy stuff, but pretty soon he's falling behind Jim, who just saves his up for advancements (and can then, relatively speaking, do the splashy stuff better WITHOUT the expenditure). Now, if saving your XP ultimately COSTS you more XP (because of how it is earned) that might bring things back into balance. It would, however, seem to still fall to the core of
@Aldarc's objection, which IIUC is that you are discouraged from doing cool stuff.
I don't really see the draw of forcing this sort of meta-game level resource dilemma on the players anyway. Wouldn't it be better to run the resource game at the fiction level?