Kris

People need to stop perpetuating the Ork belief manifestation bit. All Ork belief does is slightly amplify the effects of something. A waaagh can't believe stompers into existence, but their belief that red things go faster does make them go slightly faster.

Frieza seems a much safer choice. Cell could theoretically just keep getting stronger to the point he'd be uncontrollable. Unlike Frieza, Cell doesn't care about conquest and might wipe out whole planets out of boredom. Frieza at least wants people to be around to rule.