Since morals are off and they're bloodlusted Stark could likely take out the paths before any of them get the chance to transform. After that it would be a case of cat-and-mouse between him and Obito; Stark has nothing to get around Obito's intangibility, but Obito can't really do a thing against Stark. Under these circumstances I say that Stark wins after a very long, drawn-out battle.
Had it been their normal versions I would have given it to Obito, as the paths would have had time to transform. As strong as Stark is, I don't see him surviving long against multiple mountain-busters whilst also avoiding being sucked up by kamui.
Holy hell Obito stomps, not only Starrk have no way of getting past his kamui, the Jinchūrikis are no slouch either.
Fully transformed Bijuus solo this, or Obito solo himself.
Read previous posts before you comment, namely the one where I showed that what you're suggesting wouldn't work.
9 Tails is a multi-mountain buster not just mere mountain. All other Bijuu are at least mountain busters. Well technically we haven't seen Shukaku's bijuu ball.
I dare say R2 Ulquiorra is above Starrk anyway. Not to mention there is that Hueco Mundo reiatsu boost.
Not that it matters who wins but point of clarification, but aren't Tobi's paths supposed to be treated as Edo Tensei paths?