Brave New World is about 600 years in the future. Fahrenheit 451 is like 1984, it's about the near future, the 'next thing'. That's more scary to me.
Brave New World has even fake human birth and genetics. People aren't even born in the usual way, and their fate, their caste, their whole life, is decided before they're born. So humans are somewhat less human. It's a whole different idea of civilization.
Fahrenheit 451 is about people just like us under one more increment of how things are going now. But banning books is not as scary of a thing as it once was, partly because nobody reads books anymore. Millions of books have been digitized now and they will be impossible to wipe out completely. That's not nearly as scary as your genes being manipulated before you're born to make you stupid.