Well, if Obito has MS, then no question he would lolstomp Itachi, and save the clan
If he didn't have MS (because rin never died) then it's an open bag. We don't know how strong he would've been and even Itachi has only recently gotten MS, so it's unknown whether Itachi could've used Tsukuyomi or Amaterasu proficiently enough to fight Obito.
Overall, I would say, Obito wins, he would've been much older, and even though Itachi was a prodigy among prodigies, Obito had more experience so I'd give the win to Obito