Idiocracy, simply because it isn't aliens/subliminal messaging implementing the dystopia. The effects are more exaggerated in Idiocracy (we don't actually have garbage avalanches or public executions by gladiator), but the collapse to the lowest common denominator and the disdain for intelligence is real.
Both are great movies, but I'm gonna go with Idiocracy because if They Live was true at all then that is scary af. Idiocracy accurately predicted the dumbing down of the general populace, but if it were realistic, there would still be a group of smart elites running things instead of this guy:
The aliens in They Live are a metaphor for capitalist fascists…who are using subliminal messaging (leveraging algorithms and social media) to influence people. Also note the tent cities in They Live.
Both movies are true and were social commentary of how life was when they came out. So of course they’re still true today. They’re a reflection of the human condition, not some warning of impending backsliding into ignorance. Collectively, we were always rolling around in the mud being ignorant. tldr it’s always been this way and it always will be.
They Live. By far. Edit: If you think it's Idiocracy, you're part of the Idiocracy. You need the They Live glasses to see that everyone is part of the Idiocracy.
Mike Judge on using crocs in "Idiocracy". The wardrobe woman had a limited budget. [...] So we shot it in 2004. She goes, she tells me, okay, there's a startup. And it was Crocs. But they weren't out in the world yet [and] she goes, look at these horrible plastic shoes with holes. She said we could really save a lot of money. Just put everyone in these things. I said, well, but what if by the time the movie comes out [...] these become popular and people are wearing them? She said, oh, these are never going to become popular [...], these things are horrible. [...] Then it took two years for the movie to come out. By then people are going like, oh, that's pretty funny that you put everyone in Crocs.