Trailrunning is less harsh on joints for sure, but certainly not easier based on the times of anyone who's run trail vs road events over any distance.

Mud, obstacles, and terrain that hasn't been bulldozed and rolled to be pan-flat make it much slower.

I'll take that excuse for slow runs! But seriously, I don't run in training for speed, I run for fun and for fitness. And the uphills on the trails certainly help with that.