Hidan’s immortal but like Elder Toguru he is susseptable to illusions. All Tobi has to use is basic sharingan and trap him in an illusion….or he could just use Magekyo sharingan and make him dissapear. Tobi wins.
Now this is a battle. They are both First Class ninja who are excellent at genjutsu. They both have also learned much about the sharingan. They are both Uchiha and are arguably the strongest Naruto characters in existence. It’s hard to tell who’s stronger since they’re about even in everything. I pick Itachi because he has the hand to hand edge. Itachi wins.
Update as of 03/01/2017 the verdict has been changed. Obito has completely surpassed Itachi by the end of the series and made the gap in their abilities considerable. Obito is physically on a whole other level and the fact that he also possesses the sharingan assures that Itachi won’t be able to pull any genjutsu tricks over him. Obito wins.