BotW for me. My main draw is exploration, discovery and world building. BotW did that better than TotK.
First of all, re-using the map was a let down from the start, removing most of the incentive to see what's on beyond that mountain etc. The Depths redeemed that lack of new discovery, but in the end lacked variety. The Sky islands felt like an after thought, while the caves felt repetitive and were all too bright. What were those bright blooms for... (To sell when reaching 999 limit again and again)
Secondly, BotW's landscape was made for its quests and exploration. TotK put some new (good) quests over it yet they obviously weren't as well integrated in the landscape as in BotW. Plus a lot of left over BotW world quest furniture stuck out in TotK. Also being able to simply launch and fly anywhere made exploration trivial, not rewarding anymore. As well as approaching a lot of things in the wrong order and from the wrong side.
The temples in TotK were even more lacking than the divine beasts in BotW. However the approach to the temples was done really well, if you encounter them in the right order that is and refrain from simply flying to the temples. The lightning temple was the only one that felt coherent, albeit still small.
Ultra-hand was fun to use but ultimately broke the game more than adding to it. Shrines didn't feel rewarding to solve since you could cheese most of them with ultra-hand and recall. The 'puzzles' were all very simple anyway, didn't get stuck once. The combat shrines were a big improvement over those in BotW and actually better puzzles than the puzzle shrines. Yet there were too many Rauru's blessing and the shrine quests were very repetitive. Finding and solving shrines was better in BotW.
The fuse system is fun and very useful though. Unfortunately the UI is a piece of crap, so much time wasted looking for things, swapping armor pieces and so many unnecessary steps to get things done.
It's telling I enjoyed TotK the most while ignoring Zonai stuff. Doing the Princess sightings and other stable quests on horseback, not using the launch towers, following the roads, not using fast travel, not using ascend. As well as exploring the depths on foot, no hover bike. Suppressing the blood moons and clearing the land of enemies.
TotK certainly had many improvements and some new fun things, yet ultimately BotW is the more complete, balanced package. I wouldn't replay either though, costs way too much time.