Having hiked the CDT, PCT and AT, I know the CDT is the best. The CDT, especially through Colorado, has some of the most rugged terrain in the world. The PCT is nice, just too well defined which makes it too easy, no challenge. The AT is hardly in the wilderness, in addition, the heat and humidity of the east is offensive and intolerable. The lack of a completely defined route on the CDT, the altitude and the rugged nature of the Rock Mountain backcountry, make it the winner hands down.