If you are going to put the same amount of fuel is one thing.
The advantage of why you can use alcohol to get more power is because you can put more fuel in a cylinder and it will completely burn. Where extra gasoline won't get burnt and will go out the tail pipe.
Why do alcohol dragsters go faster?
Is it because alcohol weighs less then gas so the weight reduction makes them faster?
Or is it they can get more power out of alcohol?
Yes different fuels have different btu producing ability. That fact alone is misleading because ignores what can be done in the real world.