Different situation might make someone favor one over the other. For example if a room is cold, you might need belly heat since you can get more surface area heated, compared to back heat. If getting your ambient temps up is not an issue, I have found back heat to be more consistent because there is no substrate on top of it ( I use cypress), just the back of the tub. Also it doesn't get worn out from a sliding a tub
There is not a need for belly heat for feeding or digestion.
While I have never used them, I made a thread asking for the cheapest thermostat: this seemed to be the cheapest one recommend by some: http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S Not that it makes it a good thermostat, its not proportional, no night drop, no mechanical safety, no other features at all pretty much, but it much better than going unregulated.