Flagstaff/Fredonia route, but, weekend Vegas traffic and Spring Break probably account for that. My MIL lives in St. George so we visited her going down and on the return. We went down to Phoenix through Vegas on Sunday and returned through Flagstaff/Fredonia (with a bonus view of Colorado City ) on Friday. The Hurricane/Fredonia/Flagstaff route is the more scenic of the two. Time wise, the difference was not enough to make that the deciding factor although, despite being longer in miles, the Hurricane/Fredonia/Flagstaff route was faster due to traffic issues on the other route.