For transmitters, I'm firmly convinced that slow discharge NiMh such as Eneloops are far superior to LiPo's for the following reasons. First, you can charge them in place (no need to remove from transmitter to charge); second and probably most important is that when you forget to turn off that transmitter switch (and that will happen) you will not destroy the cells. Third, you can use a simple constant current charger and you won't have to worry about overcharging as long as you charge at 0.1C. The modern slow discharge NiMh's hold a charge nearly if not totally as good as a LiPo.