Hey - I'm running a marathon this fall that has road and packed dirt side by side for the middle ~11 miles. For training I tend to stay on the dirt (less impact), but I'm curious what you think is best during the marathon itself. If it's dry, dirt seems softer/less impact, but may absorb some speed (longer time spent on the ground each step).
Probably ~3:10 pace, running in a lighter/less padded shoe.