Every has been saying that Oro would win due to the fact he would keep regenerating,
well I'd like to ask one thing. Doesn't any jutsu use chakra? Remember when Sasuke used it against Itachi? The regeneration jutsu uses alot of chakra and isn't exactly fast, it took sasuke atleast a few seconds. Took Oro longer to do it when he fought naruto in 4 tails mode. Every also says oro has all these jutsu and can use edo tensei, but A is extremely fast. Remember when naruto in 3 tails mode on the bridge punched oro into the forest and he didn't even have time to dodge. A is even faster than that i'd say, and if he fought with orochimaru, oro wouldn't even have time to use any jutsu's or summons, A would probably lariat him and so on, forcing oro to try and regenerate till he had no chakra left. In the anime, if this happened, Oro would probably run away before he died. But if we are talking about a fight to the death, oro's chakra would run out way before A's due to having to regenerate all the time, if he somehow managed to hit A with an attack it would likely be knocked back by his armour, and as "MATAHARI" said that he would summon A's father, the third raikage to fight A, how do you know Oro had some of his remains, yeah, kabuto did, but it never said Oro did, so as far as we know, the only people who oro could use edo tensei with are the first and second hokage.