I believe lower cadence uses your leg power more and less of your cardio power, while higher cadence saves your leg muscles and uses more of your cardio… which makes sense why you would use higher cadence on the bike leg of a tri…
So it all depends how strong your cardio system is versus your leg strength.
…
Lance’s notoriously high cadence could also work for you (but maybe that was due to doping!).
Actually, Lance (via Ferrari) seemed to subscribe to just that theory:
" explained how a faster cadence put less stress on the muscles, transferring the load from the physical (the muscle fibers) to a better place: the cardiovascular engine and the blood." (The Secret Race, p. 104)
And of course Ferrari (allegedly 
) helped with the blood management.