I've done the Cohutta and the 101. The 101 is definitely a more challenging course. The 101 has steeper climbs and lots of them. Cohutta has more long gravely climbs that go on forever. Plus the 101 singletrack is more challenging at the 101. They are both great races and I think the 101 is just more fun. I haven't done the shenandoah yet, I'll be there this year though.