Honestly, neither of these characters appeal to me.
Oden is naive, gullible, stupid beyond belief, completely disrespectful (“Hey, how about I use this dead guy’s cremation pyre to cook my food? Who cares if his entire family is distraught, crying and demanding I stop? I do things my way damn it!”) and starts conflicts for no reason (seriously, Harem Wars? Really?).
His introduction was the worst first impression I have had for a protagonist character since the time I read the Afro Samurai manga (nothing beats that shit show).
Despite being an utter degenerate, nearly everyone loves him and those who do not are apparently evil and/or stupid. Yes, let us praise the man who trusted a liar and a criminal infamous for brutality to keep their end of a bargain and not just strengthen their grip on the country. Very good.
On the other hand, Orochi is grossly incompetent. For a man consistently concerned about rebellion, he sure goes out of his way to be as detestable to the citizens of Wano as can be possible. He is destroying his own natural resources and killing his own workforce. It is a miracle that his country actually has a native workforce and an economy by this point.
Just compare that to Linlin who is so beloved by her citizens that they are willing to literally offer a portion of their own souls on a regular basis and put up with her periodic berserker tendencies.
Say what you like about the Big Meme but at least she knows how to run a country.
Ultimately, Orochi works better as a despicable, unforgivable villain than Oden works as a flawed protagonist so I guess I will vote Orochi.