Ignition! devotes an entire chapter (Chapter 7) to the topic of propellant performance. One crucial point is that you are aiming for as high an exhaust velocit

Ignition! devotes an entire chapter (Chapter 7) to the topic of propellant performance. One crucial point is that you are aiming for as high an exhaust velocity as possible, and that means that all else being equal you want exhaust products with both a high heat of formation and low molecular weight. It's not just about the energy balance (not that ATP is particularly outstanding on that measure anyway).