I really like Koko. He's got a pretty unique typing (only two Pokémon have it), and the fact that his hands are also beaks just sold it for me. Yeah, I like birds. Totally not biased here.
Tapu Koko is my favorite. Party because I like its design and party because of its role in the story and connection to the main character.
Tapu Fini was definitely my favorite because it's a pretty mermaid lmao. I really like it's design with its delicious color scheme.
Tapu Bulu gets my vote! I love the design and its grass type moves under Grassy Terrain hit like a freight train
Tapu Koko is my favorite since it’s fast and it can hit hard, and it can be physical or special. Fini is a close second because of design, and its mysterious-sounding cry.
I'd rather specify my least favorite, that being Koko. I like the other 3 equally, tho. If I have to choose one of them I suppose I'll stay with Bulu because of its grassiness.
I'm going to say Tapu Koko just by its appearance and aesthetic alone; next in line I would choose Tapu Bulu.
I'll be honest, I don't really like the tapus. My favorite would have to be Tapu Lele simply because I don't like the other tapus. I like Lele better because its a psychic type, and looks less stereotypical compared to the other leles, it looks just neutral. Also, although I cannont find where I heard this before, but I heard that its scales will cure anyone sick and harm anyone not sick. I couldn't find where I heard this so take it with a grain of salt, but Lele has been known to be guiltless and cruel. I like the idea that the creature of life is rather indifferent to suffering, it adds more to its character than just a pretty face.
I like Tapu Bulu because it looks like a bull, and you wouldn't think by looking at it that it's a fairy/grass type.
Least Favorite to Favorite, all in my opinion - Tapu Bulu - Something about Tapu Bulu's design just screams "unappealing" to me. The way its body is shaped and the bizarre look of its shell when opened up just make it look like there's something wrong with it. I've used it competitively for its typing and stats before and it's definitely a fun mon there, but nothing I'd ever get excited to use. I don't HATE this one but it's not one I really like. Tapu Fini - Kind of middle-of-the-road for me. I like it, but it doesn't stand out in any way to me. Its design is good, but it doesn't really knock if out of the park for me. I've never used it competitively before, but I'm sure that as of now, it wouldn't be something I would dislike using. I think this one's good, but I just really like some of them a lot more here. Tapu Koko - This was one of the Pokémon I was most excited for coming into Sun and Moon. The Pokémon that had been revealed at the time Tapu Koko was hadn't been all too interesting to me for their own seperate reasons, and this was the one exception. This thing just looks awesome, and it's decently fun to use competitively on top of that, or it was in Gen 7 at least. What's not to love? Tapu Lele - When it comes to recent generations, I on average like the cooler ones a lot more, but there's always a few cute Pokémon that I end up liking more than anything else. That's Tapu Lele here, basically. Even if it wasn't cute, I think the way its shell works is more interesting than anything else; its hair things pop up to make antennae that make it look like a butterfly emerging from a coccoon. I also love using this thing competitively, it completely rips apart a lot of defensive teams unless they have one of few specific Pokémon.