My friend races R/C cars so he knows a lot more about batteries (since we both use the same ones) than anyone I've ever known. He laughs when he sees us airsofters using anything but brand name (Intellect, GP, IB, etc.) and just cant get by why people use NiCd's.
Personally I'm looking to get an MP5k and I'm getting Intellect 1400mah NiMh batteries, no memory, higher mah so longer life, brand name quality, and only costs a fraction more than cheap ones but are better in every way and will have a longer life (more charges/discharges before it dies).
Personally my advice, and his, is to just put in the extra little bit of cash and get good batteries. They have em at WGC, redwolf, and at
cheapbatterypacks.com
Large battery packs in airsoft use sub-C batteries (SC) and as far as I know the mini and stick types use 2/3A. When I get some cash I was going to order up two large batteries for my G3/SG1 and two stick batteries for my MP5k when I get it, my friend wants to get in on it to save some shipping, was thinking of maybe doing a group order. The custom packs are a little more expensive than from WGC but they are shipping from the states, not asia, so in the end it should be cheaper.