This is a section of road on one of our rides where we get to pick up some speed and hold a good pace on the bike with a smooth cadence while holding the power down.
Cycling to a high or low cadence is something that each cyclist needs to work out for themselves, i find that holding a higher cadence allows me to go for longer without getting fatigued, when i go on a bike ride i try to keep my average cadence over 90 this way my legs don't build up with lactic acid to quickly.
I mainly go with what my power meter is saying but i also like to see my cadence on the screen of my Garmin 510 edge, so the only readings i have on screen is Power and Cadence.
If you don't have a power meter then you may want to go with your heart rate so understanding you zones is important and you can combine this with your cadence to get you to a good average speed, but a power meter is the best way to measure efforts when cycling.
It's also important to take the time to look at your data that you upload to Strava or Garmin, by understanding your data reading you will be able to gain a good idea of the sort of zones you can hold whether your using a power meter or going on heart rate.