NiCad (1910, 1899 origin) is old school battery tech that had fast charge times, good temperature stability and high cycle times, but suffer from memory effect and were not environmentally friendly.
NiMh (1989, 1970 origin) is the current standard of simple rechargeable battery types and has higher capacity, can be charged many times, but have very fast transitions of voltage (When power is low it fades FAST).
LiPo (1997, 1970 origin) is the current generation of high energy density battery. Higher more stable power output, but the chemical reaction of the component parts results in "Puffing" (electrolyte decomposition). Limited cycle life.
I personally use Lipo's and still have a plethora of NiMh batteries.
(5000 MaH NiMh runs my KV-1 for an 3/4 oh an hour, 5000 MaH LiPo runs it for 2.)
Some rules of thumb: (Ignoring NiCd, since it is toxic and not really used anymore...)
NiMh: Run them from 100% to 0% before recharging. Reduces memory effect. In the tank, usually the sound starts to go wonky when the battery power is low.
LiPo: Make sure to connect a battery alarm. Lipo's generate heat when they have current overdraw (not likely with our tanks) and when there is resistance in their cells (caused by delamination of anode/cathode layers, aka electrolyte decomposition). Aka the more puffed they are, the more puffed they become when used. There is NO way to stop the decomposition. Use proper chargers, and inspect your batteries.
A good thread for LiPo's.