Each AAA battery is 1.2 volts (rechargeable, otherwise 1.5) and if they are connected in series as they usually are in electronics that will add up to 3.6v vs just 1.2v of your lonely AA battery, even if their amp ratings are the same. This little equation might make the picture clearer:
amps x volts = watts
And also bear in mind that if you have multiple batteries in a bank, all will be downgraded to the state of the weakest one. It is better to have fewer batteries of higher capacity in a bank.