On my bike with lots of gear choices I mix it up a bit, working on getting my cadence higher sometimes, working on increasing "power" in a too-high gear other times. Lots of opportnity for the latter when climbing with a slower rider, but wanting to stay with them.
On the fixed gear bike, the slow cadence power-push is demanded on the climbs while the high cadence practice is demaned by the descents. So fixed is good since it really doesn't give you any choice but to practice both.
Rick / OCRR