What you don't usually see in the packaging of different rechargeable Ni-MH batteries (the most common nowadays for AA, AAA of 1.5 volts and 6F22, 9 volts) or in promotional efforts, is the high rate of self discharge. These batteries are a complete loss of energy, they could be called self dischargeable batteries. With numbers according to Wikipedia of 5-20% the first day and 0.5-4% per day or more in high temperature scenarios. Worst case 20% the first day and a month at a 4% rate per day it's a lamentable figure.
Low Self Discharge Ni-MH rechargeable batteries come to aid in this great issue that cause misconceptions about rechargeable batteries, inconveniences and a waste of energy. Some LSD versions with the ability to retain up to 90% after six months and 85% after a year.
LSD Ni-MH seems to reach these capacities:
AA: 2450mAh (Sanyo Eneloop Pro)
AAA: 950mAh (Sanyo Eneloop Pro)
6F22: 230mAh (9.6V Imedion)
Interesting how rechargeable batteries in the AA format compete with most of the alkaline batteries around there and retaining as well the capacity. If rechargeable batteries provide up to 500x cycles in this rational LSD version, the choice is a must from any perspective.