Well the thread had already been made. Most sided with Neji but the only ones who said Kakashi was Joki and some Kakashi fans.
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I'll go with Neji to because fighting him close range is extremely deadly and I don't think kid Kakashi was a long ranged fighter. Also Kakashi himself admitted that as a kid, he was a fool so Neji has the edge in battle smarts. Even Obito also called Kakashi stupid and Obito wasn't too intelligent as a kid either.
Rotation is a pretty good defence and I think Kakashi won't be able to get Neji. Also Neji could outlast Kakashi as Neji has pretty good stamina while Kakashi's is average at best. I don't think Kakashi could use chidori as effectively ash he can now so his chances seem quite slim. If he did have the rasengan, I guess he could try using that against Neji's rotation and it may penetrate due to the rapid spinning momentum of the chakra in the rasengan which may counteract rotation.
I don't know much about their speed but I'm assuming Kakashi has the edge in that regard. Taijutsu obviously goes to Neji while ninjutsu obviously goes to Kakashi.
Saying kid Neji would lose because kid Kakashi was jounin is wrong since not all jounin are at the same power level neither are all genin at the same power level. Also bare in mind that Kakahsi became a jounin during a time of great need and when man power was low due to ongoing wars to so it was relatively easy to get promoted unlike during the part 1 chunin exams where there was peace and not a lot of jounin were required as there was a surplus of them. In that case, Neji's generation had a harder time getting promoted because the demand for high level ninjas was rather low.