My completion track record:
3 for 3 Full Marathons, 15 for 15 half-marathons
0 for 2 Whitney Summits
(1 over-night, 1 dayhike)
My vote:
Whitney is tougher. Big reason is the altitude, terrain, and lack of any support stations along the way. (A good marathon has water/aid stations every mile or two)
If your friend starts comparing Whitney to ultra-marathons (100+ miles) then my vote may change...but not likely.
