The lipo would last longer same size.

Lipo doesn't have so much internal loss (heat) as a NiMH - that heat the NiMH makes is used to make amps in lipo. Lipo does hold its voltage under load better as well. You can approach that characteristic with very carefully matched and maintained NiMh pacs, but compare d to average NiMH pacs, lipo usually has higher voltage under discharge.