You have to go with your strengths. Depends on how you are built. I don't have mashing power for example. I do however have good cardio. I find if I spin a shorter gear, it saves my legs and the extra wind it takes doesn't bother me. By contrast, spinning at high RPM for prolonged distances might wear down a masher for the opposite reason...they can't bear that level of cardio.
Depends on the rider as to what works best. It is no coincidence that Lance was a spinner and Ulrich is a masher...what works best for each of them.
George