There isn't any "Best" battery. It all depends on your requirements.
Rechargeable, Non-extreme temperature:
Low cost, high weight- Lead acid types, SLA & AGM are good since they can be mounted in any orientation.
High current discharge, medium cost- NiCd
High capacity, medium cost- NiMH
Low weight, high capacity- Lithium types. LiIo or LiPo
Also consider the charger since long life, full capacity and safety is dependent on proper charging.