The shortest route is right up the 93. Outside of Phoenix the 93 becomes a lovely 2 lane road. It is an easy straight drive but passing or being passed is problematic is that issue bothers you. The 93 up to Las Vegas is now ok since they opened the bridge that bypasses the Dam.
A longer but less stressful option is freeway all the way. Take the 17 to Flagstaff. Then the 40 to the 93. It will take a bit longer but there are plenty of places to stop and stretch along the way. It was a long drive the many times I traveled that way in a car. The many MH drives were really too long for me. I would rather drive from Tucson to Williams, spend the night and take the next leg up to Las Vegas.
Enjoy and Happy Trails.