The most notable difference, as mentioned, is the size, with AA being the big brother out of the two. AAA is more slender than AA, which is also taller height-wise.
Typically the same, each cell will have 1.2 – 1.5 Volt range. You will note little difference in the power between the two initially.
AAA and AA batteries produce the same voltage (1.5 V). AA batteries have about 2.5 times the capacity of AAA batteries, so they’ll last longer in any particular device.
When it comes down to the choice between Duracell and Energizer, there’s no outright winner. Both brands use the best technologies and aren’t significantly different in any other features. Whether you want to go with Duracell or Energizer is a matter of preference.
Most AA and AAA rechargeable batteries are made with nickel metal hydride (NiMH), as opposed to the nickel cadmium (NiCd) batteries of yore. NiMH rechargeable batteries hold a charge longer, can be recharged more times over their life spans, and have higher capacities than those made with NiCd.
If you’re out of AA batteries, did you know you can use a smaller AAA battery by folding up a small bit of tin foil and inserting it on one of the ends? It totally works since AA and AAA batteries carry the same amount of voltage.