General differences between ninja and benders to be considered; Benders have a more natural relation ship with their powers not having to take time to weave signs. Dare I say, their hand to hand is more fluid than the straight forward punches and kicks that many ninja use. Of course ninja can get away with that because they tend to be much much faster in straight bursts, and they generally seem to wield a greater array of abilities, and raw power. Of course these two aren't typical. Sage mode and avatar state could be taken into account, but I can't really imagine these two going for each other's throat to quite that degree. Your standard case of mistaken alignment could allow for a pretty fierce fight between them before it was broken up, or maybe later they come to respect each other enough to spar at full power. What do you think?