In reply to purplemonkeyelephant:
> Using the flat base of the pot puts the burner closer to the contact surface, does that reduce efficiency?
Having the flame too close to the pot does reduce efficiency. It seems that the pot cools the flame, resulting in incomplete combustion. As well as fuel consumption, carbon monoxide emissions are also increased and could be harmful in even a partially enclosed space. It is reportedly a design fault with many of the micro stoves on the market.
To work properly, a heat exchanger needs to be a reasonable match with the stove. There is something to be said for the smaller pot. Apart from being lighter, it is much easier to get hot and you can have a drink while you are waiting for the next one.