Update: This article is out-of-date, please see my 2015 review.
Sanyo’s Eneloop batteries have had an edge over other rechargeable AAs since they were released in 2005. Basically, Eneloops could retain their charge longer than other rechargeables, including other low self-discharge AAs. Eneloops can hold 85% of their charge for one year, and 75% after three years.
Now, Sanyo has released a new version of the Eneloop, called the Eneloop Pro (in Japan) or Sanyo XX Battery Powered By Eneloop (in the US and Europe). The Eneloop Pro battery has a capacity of 2500 mAh — which is 500 mAh more than the regular Eneloop. In informal tests, Eneloop Pro retained 2035 mAh of capacity after 7 weeks of storage, which was higher than any other NiMH battery (both regular or low-self discharge), making it the longest lasting rechargeable AA battery. The only other battery to come close was the Energizer Recharge, which retained 1859 mAh after seven weeks of storage.
Sanyo hasn’t released an AAA version of Eneloop Pro.