One of the first major clashes in this duel, combat in both Horizon and Breath of the Wild is fantastic.
The latter is certainly the same 'lock on and evade in four directions' you've come to know and love from Zelda, but now there's a more accurate and useful parry system, a last-minute slow-motion dodge-flurry and a number of special abilities you'll frequently bust out. Atop this, Breath of the Wild has a very in-depth and fun system of elements to play around with. Rolling boulders down cliffs, setting fire to forests, electrocuting bodies of water, severing a tower's supports with some well-placed bombs - there's an inherent feeling of mischievous experimentation present throughout.
For Horizon, each and every creature you'll come across requires a specific pattern of attack to bring down, allowing its otherwise Shadow of Mordor/Assassin's Creed-style bow n' arrow/hide-in-the-tall-grass basics to flourish. You'll set trip-wires for charging creatures, target specific parts to disable their most damaging attacks, lob bombs from afar, wade in with your spear, sever weapons and use them yourself - it really is quite staggering, and when you're up against a number of enemies at once, elevates any battle into a blur of in-the-moment improvisation and attempted best-laid plans.
This is one HELL of a tough category, both games really are incredibly solid, but thanks to Zelda's occasionally unreliable targeting and stealth mechanics that fall down in group encounters and one annoying story section respectively, Horizon just edges it by remaining consistently solid throughout.
Winner: Horizon Zero Dawn