You're all idiots. :|
Zabuza's taijutsu and kenjutsu are worthless against Suigetsu due to Hydration Technique.
Suigetsu has been proclaimed, "The Second Coming of the Demon," and was trained by Zabuza. Thus, he is naturally familiar with Zabuza's hidden mist capabilities. Not that this matters since Silent Homicide Technique is worthless in this fight.
Suigetsu has a blood line. To be more specific, a water blood line. He possesses a jutsu that can rival B in his full eight tails transformation in terms of physical strength. And to those of you saying that Zabuza can take hits so he'd win, Suigetsu was able to take a TBB and live. That's far more impressive then taking a few spears in the back and then dying.
With the above said, Suigetsu clearly has a better mastery of Water Jutsu than Zabuza. The extent of Zabuza's powers seem to be around the Water Dragon and Giant Vortex level, whereas Suigetsu has already surpassed that with Great Wave Crash alone. And chances are, we haven't even seen him at top form as of yet.