Belly heat here...one strip on each shelf all controlled by one unit. Each strip is the exact same length. I have each strip wired with a plug individually however so if I needed to I could have a different heat setting on that shelf if needed or for cycling snakes that will be bred.

For ball pythons it seems to me belly heat would be "better" for a couple reasons. They need the heat to aide in digestion, which they can directly access with heat directly under the tub. I also would think that belly heat would be more efficient for heating tubs since it will rise directly into the tubs heating both the "ground space" and the ambiant space. I tried back heat for a very short time and I had to crank it up quite a bit higher to before the tub temps got remotely close to the same as they did with under heat. In both cases the room was at a constant 80F or slightly more. I run belly heat and keep the room between 78-80.