Bike fit will also make a signifcant diference - like seat height, saddle fore/after adjustment and handlebar reach/height. You have to adjust it to either a shorter or a longer crank, each time you swap the cranks, even if just for trying what you like best. Otherwise the diferent cranks might produce irrelavant or misleading results. Aditionally, some people just do feel better spining (shorter cranks) while others wouldn't trade lower cadence for anything else.