If the weather is clear then a great option would be I-40 to Holbrook, then south on highway 377 to highway 260 to Payson then highway 87 to Phoenix. All are good easy roads. 87 is mostly 4 lane divided. Total mileage is 775 which would be the shortest route. There are a few grades but mostly downhill. This would be the most scenic route but avoid if theres a chance for snow. A good place to stop for the night would be at Eagle View RV located on 87 on the outskirts of Metro Phoenix, about 380 miles.
I-25 is 860 miles, I-40 to I-17 is 820 miles.
If snow is in the forecast then the only real choice would be I-25 to I-10 to I-8.
