Fine, I'll explain more why I think Zelda looks better and it's synonymous with the gameplay too.
Basically, Zelda looks more alive and interesting than Horizon both aesthetically, its art style, and in direction. The game isn't as technical visually as Horizon, no doubt about that and Zelda does have flaws and ugly texture here and there but that really doesn't matter. The game looks beautiful enough to look beautiful and accomplish what it's doing mechanically, and gameplay-wise. Zelda looks better because what you're seeing is all possible. It isn't there just to look pretty, it doesn't exist just to be beautiful. You see this huge mountain that's beautiful, yeah... go climb that because you can anyway you see fit.
You're probably thinking "This is comparing the games overall than just visually" the thing is, BOTW visuals and gameplay actually co-exist. There are no rock formations that obviously tell you you can climb there, there are no trees with sore thumb branches telling you can climb it, there is no visual indicator you can cut something down, light it on fire, or use it. It existing is your visual indicator. Am I saying BotW has no restrictions? No. But we've yet to see anything typical of an open world game and it's art style compliments all of this. Seeing and doing are two different things, especially in video games. That rarely looks to be the case in BotW. Seeing is doing and doing is seeing.
Horizon has yet to display anything of that level in all the footage we've seen. That's a beautiful mountain, can I climb it? I doubt you will be in Horizon, we'll see, but I doubt it unless there's a set path which will inevitably limit how high and what you can do. That's why I say Horizon looks typical, it looks like something seen before, it doesn't stand out visually. Visuals only look so beautiful and can only be appreciated so much if all it is is something you can experience or explore optically. Being able to visually and physically is when it's really a beautiful thing.
But that's just me. My point may seem confusing but basically I'm saying Zelda's art style looks visually better than Horizon, and being able to interact with what is visually appealing put it above any technical aspects of Horizons visuals.