The physical size of the battery will determine the capacity -- that is
ampere hours.
Generally the AA will have a higher ampere hour rating than an AAA within a
given type -- i.e. it will last longer for a given load.
Manufacturers don't seem to be too willing to give amp/hour ratings -- one
reason being it will vary depending on the load.

However you can check url:
http://data.energizer.com/

And they have capacity charts (with a caveat regarding load)
Example a typical AA is rated at 3135 milliamp hours
A typical AAA is rated at 1375 milliamp hours


AAA batteries are ideal for the smaller devices, of course

For your application -- Buy an AC adapter -- saves on batteries when you
have AC power available.

I have a Radio Shack DX-398 and it eats batteries big time -- so I use the
RS AC adaptor when at home. Batteries are fine when traveling.

Hopes this helps.

--
73- Cambio - Keyboard To You
"Tom Welch" wrote in message
om...
What are the tradeoffs when buying
radio gear that is powered by AAs
vs. AAAs batteries?

Both AAs and AAAs seem to be priced the
same.

I have never bought a radio using AAAs,
but now I am very interest in buying a
Sony pocket radio that uses AAAs, so
I am thinking of making an exception
to my rule of never buying gear that
uses AAAs.

Tom Welch