I've had both power meters and cadence sensors. Both have value. Power is just torque times cadence. There is such a thing as an inappropriate cadence. You want good power and endurance. Run too big a gear at a low cadence and endurance suffers.
I'm too old now to care about power, but I do a lot of climbing in Colorado, and I know that letting your cadence drop below 65 isn't wise. If I'm on a climb and can't maintain 65 gpm, I need lower gears.