Actually this is not always true. For slow boats and sport use they will weight less, but for high speeds and racing the weights are about the same - in some cases they are even heavier than similar voltage NiHM cells. The problem is, if you want to pull 80 amps for high speeds you'll need to get high capacity cells and run them in parallel, adding weight but not voltage. It all has to do with the power output you need.

Some AA NiHM cells can safely discharge at 50 amps - I watched Ed Hughey set a SAW record last Spring with eight of the red GP2000 cells. But most AA sized cells are limited to 10-15 amps max without damage. Not all sub-C cells will put out 100 amps, but the best quality ones can beat that. I don't know about the Energizer cells, but I assume that they are low-power cells and would be markedly slower than decent sub-Cs. You get what you pay for....[&o]