These are two giants in science fiction, in political philosophy and in pop culture. I'm a big fan of both. Great to read a discussion between them.
First, there's the artistic stele of the books. 1984 has got this graphic novel, Noir feel to it, like Walking Dead or Sin City. Brave New World has this brightly colored surreal feel to it. It's hard to compare books that are different in this way.
Overall, Orwell's world felt more real to me, like it could have been brought about by real political circumstances. The system itself is evolved around the principle that whatever improves control survives. It feels like a political system that has devolved into its current state with the original vision or rhetoric of the ideology that brought it about remaining as a vestige, like Marxism in China.
Huxley's world feels a little more fake to me. It's like some political genius designed it head to tail and things went ahead as planned. It's like Canberra (If you go there, you'll see what I mean). That makes it feel more like a made up word to me, inorganic.
Orwell's "mechanisms," training society to gradually train their minds using language, euphemism, historical revisionism, social penalties for bad thought patterns and as much control over what people see & hear as possible… it feels real to me. We see that stuff at work now as Orwell saw it in his time. It feels possible, though I think Winston's are inevitable too. Euphemisms to control thought is stronger today than it was in Orwell's time.
Huxely's mechanisms of Soma, infant conditioning and narco-hypnosis feel less real. I can't count that against the author or the book though. Brave New World is distant future. That's inevitably more fantastical and less realistic. I think he's right though about using pleasantness over direct confrontation. Humans are pleasure seeking and denied pleasure, there will always be a force of instability.
The point where 1984 slips ahead though is the book-in-the-book 'The Theory and Practice of Oligarchical Collectivism, by Emmanuel Goldstein.' In particular, it describes how the system must allow some non hereditary class movement. If the class system is too rigid, pressure builds up as talented individual press against the ceiling. If some are allowed to progress and there are prominent examples the class system becomes less explicit and more stable. I don't know if it's some of my earliest political exposure being socialist, but that just rings true to me. I see it today. Statistically, classes are fairly rigid, but individually, they are malleable.
I'm very biased though I think 1984 is one of the most important books I read as a teenager. It shaped how I saw things.