I go up and down the east coast but I am in a small minority that travel that way. First of all if you are looking for warm weather all winter long you should go at least as far south as Mazatlan on the west coast and Tampico on the east coast. Elevation makes a big difference in weather, if you go to any mountain towns.
The problem on the east coast is there are not very nice beaches until you get to the Yucatan. Even the Emerald Coast between Veracruz and Tampico is not good.
So buy the Church book, get a Mexico map and see where these towns are that people discuss. Google them, do some research and enjoy your trip.