I agree with hsbn! The white-colored* Sanyo Eneloops, rated 1900 milli-amps, do very well for all-around use, as they keep their charge for extended periods, and are excellent performers. The higher-milli-amp Powerex batteries are nice to have when one can fully charge them right before an event, but within days, they have self-discharged quite a bit. I use both, depending upon whether I can anticipate large-volume shooting. It is Eneloops that stay loaded in the Speedlites most of the time.
I will add that a "smart" charger, that charges each cell individually, is important. I use the Maha charger model that Syl Arena recommends. Not only does it keep my Eneloops and Powerexes working optimally, it resurrected some assorted older batteries my wife had thought were dead.
Syl Arena explained it this way, as I remember it: the cheap chargers will charge until the weakest cell can hold no more, then switches off, so the several cells can only perform as well as the weakest one. An advanced charger, that charges each cell individually, provides each cell with a full charge.
*The standard 1900-milli-amp Eneloop color is white. Some sellers stock them in special colors.
