Scenic Byway 12 leads all the way from Capitol Reef NP to Bryce NP (map). I have not seen many of the other byways, but among the ones I have seen, this one is the most spectacular. What makes it also very special is that there are not that many other people traveling on it, so you can take your time and experience it in the speed that most suits you. You can easily spend a full day traveling on the highway, as there are many points of interests along the route that you might wish to explore.
Beautiful scenery becomes even more spectacular during autumn:
Driving along the Hogback is an amazing experience. It is difficult to capture it on the photo, but the road is very narrow here and goes along a ridge with steep drop-offs on both sides:
Head of the Rocks / Escalante Canyons:
Red Rock Canyon, UH, on the way from Bryce to Cedar Breaks: