My reasoning is, AAA or smaller use alkaline, they start off 1.5 volts and last a very long time. (if you use nimh, they are only 1.2V). AA or higher: use nimh

My reasoning is, AAA or smaller use alkaline, they start off 1.5 volts and last a very long time. (if you use nimh, they are only 1.2V). AA or higher: use nimh or li ion instead, those are generally more power hungry devices.