Which to use, NiCad or NiMh? You will save about 20% weight for equivalent milliampere hours by going with NiMh, not a very big savings unless you are into really small aircraft. You will get twice the lifetime from NiCads vs NiMh and a slightly lower internal impedance from NiCads. As to peak current draw, the microservos also have rather high current drains when heavily loaded, usually about 1 to 1.5 amperes at stalled conditions. So, if you are at the border line on current draw, there will be a definate advantage to go with seperate receiver batterys, type depends on your particular requirements.