I love open world sandbox games with RPG elements, so all things being equal they both would have potential for me to enjoy. However...
Horizon looks way more exciting to me. It's a unique setting. Post apocalypse itself is not unique, but the rest seems really intriguing.
Zelda on the other hand I feel like has long ago lost most of it's luster. Based on track record alone, I do not have confidence in Nintendo to finally create a 3D Zelda that bests the competition. I haven't really had fun playing a Zelda game since LTTP.











