If you don't go lipo + reg, I'd say NiMH....I use them on a glow set-up that consumes around 200 mAH on a P07, and can't see any effect on servo performance throughout the flights.
Some of the modern NiMH cells have quite a high discharge ability(mine claim 20C),and seem fine on my all digital servo 2M plane at10 1/2 lbs. dry.
I have used packs as small as 600mAH when weight has been an issue(recharging at 1C after each flight),but currently use a nominal 1100 pack,which I recharge at 1C after 3-4 flights----there wasn't any flying problem with the smaller pack, but bench reading of the voltage drop under load was a little worrying.