It took be a long time to realize this but spinning is overated. Everyone has an optimum cadence. It's based on individual builds, muscle composition, and personal preferences. Spinning is one of those old tales that hasn't died like wool is the best cold weather clothing and Italian bikes are the ebst. If spinning is claerly the best, all the pros would spin. They don't. Some are mashers, some do it briefly to vary things, some spin to recover after a steep climb, but not everyone.

My advice is try to improve spinning. If you don't get better, faster, or have more endurance, give it up. Then do what comes easist to you. I know that my optimal cadence is 90 rpm. I go to 95 occassionally, and use 80 for sustained speed. I go to 70 on moderrate inclines.