Well Kakuzu's reasons are better....He was Takigakure's cream of the crop so they sent him to assassinate Hashirama....like that would happen considering its 1) Hashirama and 2) Kakuzu didn't have Earth Grudge Fear.
Despite the fact he survived the engagement, his village looked at him in disgust...imprisoning him for his failure. They also tortures him. Being betrayed by his own home, friends, and maybe family, Kakuzu lost faith in people, took EG Fear, the elders' hearts, and fled the village.
With 91 years of life he's also become detatched from humanity....and has turned to one thing that is a constant: Money.
Obito hates the shinobi system because it caused the death off the girl she loved.
So whole I find Kakuzu's reasons better...can't say he's a better villain simply because his actions aren't being aimed at a high enough scale.