well not really sure bout that but someone should do a test between those two high end flashes. but for budget wise, the nissin counter part really bang for the bucks
Bang for the buck, yes. But to say Nissin 866 is better than SB900 is too much of a stretch.
Sure, 866 has a higher guide number. But consistency in result, refresh rates, auto FP and BL mode, SB900 wins hands down.