You mentioned Yuma which is the warmest in winter and Benson which is probably the coolest winter destination for snowbirders. We've stayed in both. Benson can get a light dusting of snow occasionally but will melt by mid-late morning. The days are pleasant.
They are completely different - depends on your needs. Yuma has more shopping and since it's a big agricultural area, can get blowing dust. It has more traffic. Benson is a laid-back western town and has a WalMart & Safeway plus small stores. If you like to do some 4-wheeling or hiking or birding, Benson has it all nearby. We're kind of partial to Benson as it was our winter roost for 10 years. We stayed at the Escapees RV Park which runs a weekly special for non-members to try it out. It's a beautiful park with friendly folks and lots of activities in the clubhouse.