Only 1 successful day hike under my belt and completed 1 marathon (in not so glorious fashion).
You can always bail half-way through a marathon and get a ride back.
Bail half-way through the hike... it's still a long hike back, albeit downhill.
When I did my day hike, I ran into hail, rain, lightning, and snow. I figure most marathons will be called off under these conditions.
Both are definitely physically demanding, specially for those that are not in super duper athletic shape (like me).
