[suicideneil]

That is the most important factor to concider when choosing which batteries to run, since a couple good 2s lipo packs will provide as much run time as 4 or 6 6cell Nimh packs. Some people even say they get bored after 45minutes or more of running from a single charge ( I would never get bored though ). The only thing to think about is the need for a lipo balancer (balances the voltage between cells in a pack), an lvc (low voltage cutoff device) which stops the lipo cells from over discharging- very very bad, and a specialised charger capable of charging lipo batteries safely & properly.

Depends on your budget and how serious you are about your bashing. That said, only hard cased lipo cells are really safe for bashing with, and on a savage conversion the batts would probably have to be mounted on the outside of the tvps, which makes them a little vulnerable for my liking. Much to consider.....