NiMH and LiPo are types of batteries. If you want a high-performance setup, go LiPo. If you're not too fussed about
speed NiMH would be the better option as they are safer and require less 'special attention'.
Also, it makes a lot of sense to get a LiPo battery if you have a brushless powered car and to get a
NiMH battery if you have a brushed powered car.
Learn more about LiPo and NiMH batteries.