Hi Ruth, both AA and AAA has the same 1.5V. But the capacity of AA is bigger than AAA.
The AAA battery is smaller in size than AA. The amount of current carrying though the battery vary in AA and AA. Typically an AA battery has 2400mAh capacity and typical AAA battery has 1000mAh capacity. The cell of the AA battery is much higher than the AAA battery. The sizes are different too.The AA battery is bigger than the AAA battery. In terms of the cycle, it depends on the manufacturer brand.
And you can find in the market too that AA battery is costly than AAA. In terms of buying in the market, either you need the AAA or AA battery, or you need both. It depends on the specific size devices that you have and how long do you want the device work for.