it really depends on what you are going to run, for intance if you were to run modified or 1/8 scale something like that a higher mah and higher C rating would be better, but if your going to run oval or road coarse, its not that critiical to have a higher C rated pack or a higher mah. A higher mah pack will give you more run time and keep the voltage higher longer, but you will still never see the full pultental of a 5000mah pack, reason being is in oval and road coarse racing, we do not pull huge amounts of amps that some of these lipo are capable of in order to see a big difference in the packs... I race for Fantom on oval, I been using a 25C pack for awile, and resently tried the new 35c pack and did not see a night and day change on the track, reason is that I'm not pulling enough amps to see this difference... I was competing against guys that ran 5000mah packs and they were not blowing me away by any means!!! The biggest thing is to think about what you are going to run, what class? then buy a lipo that fits your buget and your class from a well trusted manufacture that will help you if something were to go wrong or if you
to have any questions...
hope this helps