I've been in Southern Utah and just finished a trip to California. Mile-per-Mile, I think Utah and the Grand Canyon area wins. California's Sierras were nice, but the time to drive through the real mountainous areas really limits your time.
Southern Utah is a must see for any world traveler. So many national parks that are absolutely stunning. Arches was the one I made it to. But even the back roads through there are a sight to see.
Sykotyk