Hmm, is biking easier? It could be. Yes, you get to roll down hills or coast to take a break.
There is one effort I can use to compare, Mt. Washington.
I am no speedster at either running or riding. I ran Mt. Washington 4 times, and rode it once in the official road races. All my times are around the same, 2 hours(ish).
All 5 trips up were hard, the ride was the hardest physical event I've ever done. I don't think I'll ever do it again. The runs were hard, but I'll happily do it again, once Covid settles down.