In my opinion, Torune due to his Parasetic Destruction Insect Technique with his nano sized venomous insects, just one touch, a single poke to the head, would kill Orochimaru within minutes.
In that time of being attack, Orochimaru can use his Regeneration Replacement Technique. Orochimaru is no fool and is quite experience and knowledgeable of Konoha Clans Techniques. Not saying the experience could win him the battle, maybe, but Torune would have difficult of killing Orochimaru besides of trying to use his Venom Insects in a Taijutsu fight.
However, it is still a draw in my mind.
Torune has a chance of winning if he somehow manages touch him..and before people say replacement technique..the insect are nano size and would be in his blood stream so even if he uses replacement the insects would remain in his bloodstream.
Is it manga only at this point that he was in anbu? I never heard that.oro would know about the elite root members, being in root himself at some point. and obito explicitly knew about torunes dad. so IMO oro would keep his distance and kusanagi sword torune