I agree if they fought in Shipuuden Neji will sure be defeated unless by plot no juts, but since the scenario is way back in Chuunin exam Sasuke would loose no doubt.
1. Neji saw how Sasuke fight twice one in the forest of death second was with that partner of Kabuto that absorbs chakra so he has general idea of his fighting styles / jutsus.
2. Sasuke on the other hand was quite the opposite he never saw Neji fight & had no clue of his fighting style / jutsus.
3. Both of them preferred close combat back then & fighting in close combat w/ a Hyuuga w/out any knowledge of Jyuuken will be accommodating death.
4. Sasuke got wasted by sound 4 w/out any difficulty.
5. While Neji beat on of the sound 4 - Kidoumaru in strongest form.
If they fought during the chuuninn exam:
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Sasuke will get wasted like this:
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