I used to run in high school, intermittently in college, and as a young adult. I gave it up around the early 2000s as I just couldn't take the stress on my knees. I have don't a lot more cycling in those years as it is less hard on the knees, hips and feet.
That said, for me, running is harder, but also a better overall workout than cycling. And probably a more efficient use of time, if that is what you are after. You can be out the door for a run in just a few minutes, whereas it takes a little longer to get ready for a bike ride. And, something like a 45 minute run is a good workout, where as I would say i need to go about twice as long to get the same workout from a bike ride. But bike rides are more fun, so there is that.