Ceramic heaters cost more than uths. If you use a ceramic heater, you still need a thermostat. Ceramic heaters will also sap humidity unlike uths.

You don't need two thermostats for each species, you need one because they have different temp requirements.

A ceramic heater will also burn out and you will need to replace it. If you don't have problems with humidity, there is nothing wrong with using overhead heat to bring temps up a bit. But using only ceramic heaters probably wouldn't work so well, especially for ball pythons.

My best advice is to not listen to petstore employees. They are just trying to sell their products.