We like the Tucson area better than Phoenix because there are so many more outdoor activities that are very close--mountains, streams, beautiful Suguaro deserts, canyons, lakes. It does get cool at night and nice in the day. Jan-Feb can have a lot of 60 degree highs and 35-40 lows so certainly not near as warm as southern Florida. But the sun can't be beat and the almost always clear skys and low humidity are wonderful.
I think this sums it up great. AZ is beautiful and there's lot to do but if you want 'summer like' temperatures (or the beach), South FL is significantly warmer (IMO, winter in FL is clear with little rain and not particular humid so that's not really an issue (summer is another story)).