Think about double the amount of fuel suspended in the intake charge. The weight and density as compared to gasoline. Also think about the energy in any given fuel.

Gasoline is more power, just an issue of efficiency. Bracket motors, and forced induction work better on alky for reasons unrelated to efficiency.

Think about a basic bracket motor going from gas to alky. Double the fuel volume in the chamber and you've increased compression. Lower the temperature as well, and presto.