I am personally a fan of belly heat. That is one of the reasons that I use Animal Plastics caging for my larger cages. The heat rope that is routed into the belly of the cages. My rack system has the same heat rope in the back of the rack but it is routed into the shelf so that the gradient is pretty decent on temps in the tubs.
I like the heat source being on the bottom due to the basking area it provides. Direct contact with the heated area seems to raise body temps a bit more quickly than sitting under a light or haveing a radient heat pannel. The disadvantage is that you don't really raise the ambients as well as a pannel in the back or a light from the top. I remedy that by keeping the air in the room the snakes are kept in around 78°-80° so it doesn't require much in the way of raising the ambients in the cages.
Even in the couple of Glass "tanks" I have use the
UTH heat pad type elements. I just find them easiest to work with as far a space consumption, safety (as long as it is regulated properly) and effectiveness in raising the body temps of the snakes.
These are just my opinions and everyone will have to look at their situations and decide which strengths you want to expolit in a heater and which weaknesses you can live with.
