I prefer Sun/Moon and Ultra Sun/Ultra Moon. Ultra Sun and Ultra Moon in particular feel like much richer experiences in every regard other than the story changes.
1) The primary and most important reason is that they include the ability to use every single Pok?mon that had been introduced throughout the series since the beginning, provided you used Pok?mon Bank to transfer in those Pok?mon you wanted to use which weren't in the base games. As I've stated numerous times throughout various threads, my preferred method of play for nearly a decade has been to come up with or pick a theme to base a team around, search through the National Pok?dex list to see which Pok?mon best fit the reference I have in mind, and then breed team members with 5/6 IVs, ideal natures, abilities, and egg moves, and then EV train them all so that I can also use the Pok?mon in competitive play if I so desire. While I accept that the Pok?mon culling which took place in Sword and Shield was an inevitability, it still doesn't mean that I like that it happened. Old habits die hard.
2) Festival Plaza...sort of. In particular, Dye Houses. While in general I find Festival Plaza to be a clunky mess compared to the fabulous Player Search System from the Generation 6 games, I ended up absolutely falling in love with the Dye Houses you could get. Specifically the 5★ ones, since they allow you to choose from 3 different shades of the color that the particular Dye House you're using is based around. In an ideal world, we would have kept the Player Search System to interact with other players and the ability to dye clothing wouldn't be locked behind Wi-Fi interaction, be divided up in color selection between the Sun and Moon versions, and would just be located somewhere in the world. We don't live in an ideal world though, so this is what we're left with. Dye houses wholly redeem Festival Plaza for me.
3) Tying in with the above point, I would say that the trainer customization present in Sun/Moon/Ultra Sun/Ultra Moon is my favorite example of it throughout the series so far. X & Y had generally superior clothing in my opinion and also included the ability to choose ginger hair (an option which should never have been removed in later games), but the inability to remove the hat really hinders it for me. Sword and Shield have good clothing options and a number of nice new additions like the more exaggerated contact lenses, but I was spoiled by the Dye Houses from Sun/Moon/Ultra Sun/Ultra Moon and find Sword & Shield to be lacking in comparison.
4) While I was initially outraged by the removal of the Super Training feature that Generation 6 had given us, my anger was soon assuaged somewhat when I learned how ridiculously quickly and easily you can EV train your Pok?mon using a combination of Pok?rus, the various Power Items, and S.O.S. Battles. I'm still not all that fond of S.O.S. Battles, especially with how ridiculous they made it to try to catch Slowking and Politoed, but the speed with which you can fully EV train your Pok?mon is insane. I nonetheless still prefer Super Training since I find it to be a generally superior option for people who won't jump through all of the hoops I do (multiple 3DS consoles to trade Power Items and such between multiple game cartridges, the breeding I laid out in point #1, etc.) as well as for those who don't choose to or can't engage with the Wi-Fi functionality of the games.
5) The story, at least in the original Sun and Moon, is more interesting than anything Sword & Shield has to offer.
6) The addition of Mantine Surfing in Ultra Sun/Ultra Moon was a nice way to earn Battle Points.
7) As much as I would have preferred Game Freak to have continued Mega Evolutions through Generation 7 and beyond, I found myself really coming to appreciate Z-Moves over time. The dances/poses are cute and Z-Moves can be pretty versatile; you can go for an outright super powerful attack, you can get nice stat boosts, you can fully restore HP. Pretty great.
8) Team Skull, Po Town, and Your Boy Guzma. Tean Skull is a very fun team and I like that they're just a bunch of disaffected youths; it's a breath of fresh air compared to past villainous teams, and they feel like a team for our modern times. Po Town is cool, and Team Skull's base in the Shady House in the very back of Po Town is one of my favorite locations throughout the Pok?mon series. As for Guzma, he needs no introduction, he's just great. Both Team Skull and Guzma have great battle theme songs too.
9) Nanu. Just Nanu.
10) While I'm not all that fond of the Island Challenge when compared to having Gyms, it was a decent change of pace for one generation.
11) Ride Pok?mon are a nice concept that tie into the Alola region well.
12) Ultra Beasts are a fun concept, and Ultra Sun and Ultra Moon not only introduced more of them but allowed you to catch multiples of the ones that were introduced in original Sun and Moon. Blacephalon is among my absolute favorite Pok?mon, and I hope to acquire its shiny someday.
13) I don't have much experience with the Ultra Warp Ride, but that sounds and seems like a great feature that I look forward to trying more in the future.
14) I don't really care as much as others do, but you get to fight characters from throughout the series through one way or another like Red and Blue in the Battle Tree, or the various villainous team leaders in the Rainbow Rocket postgame event.
15) This applies to basically all of the DS and 3DS Pok?mon games and is more of a personal quirk, but the 3DS is less expensive than any Switch models. This makes trading between ones' own games a far simpler task and saves you from having to rely on friends to do things like evolve Pok?mon or transfer items from one game to another. Additionally, if you're like me and like to get multiple copies of Pok?mon games instead of restarting and losing items and progress from completed saves, 3DS games are less than $40 while Switch games are $60. More fun for less money, plus you don't need to pay for the online services.
16) Ascending Mount Lanakila, conquering the Pok?mon League, becoming Champion, and facing challengers is awesome.
17) I got way more attached to the Alola Photo Club than I thought I would. I love taking pictures of my trainers and their Pok?mon team members.
18) Great battle music, especially for the Kahunas, Elite Four, Tapus, Red and Blue, Lusamine, and some of the remixes for the past villains for the Rainbow Rocket scenario. I'd say I overall prefer the soundtrack over Sword & Shield.
Sword and Shield are decent games in their own right. I love the increased shiny chance when you have the Shiny Charm. While not as expansive as everyone seemed to think from the trailers, the trainer customization is fun as always. As someone who doesn't really outright hate any Pok?mon, I overall liked the selection of new Pok?mon introduced; my favorites of the generation include the Grookey line, the Scorbunny line, the Rookidee line, the Galarian Zigzagoon line, the Impidimp line, the Hatenna line, Sinistea and Polteageist, Snom and Frosmoth, Clobbopus and Grapploct, Falinks, Flapple, Perrserker, Galarian Farfetch'd and Sirfetch'd, Galarian Corsola and Cursola, Stonjourner, and Zamazenta. There are characters I like, such as Marnie and Piers. The Wild Area is somewhat fun to explore. I love the Glimwood Tangle area. Oh, and the soundtrack is pretty good too.
Regardless though, the faults of Sword and Shield outweigh their strengths for me. I said enough about the Pok?mon culling in point #1 so I'll leave that be for the most part, but suffice it to say that it does hinder my ability to engage with and enjoy the games as much as I'd like to. The story and world feel pretty bland, and calls into question why I should care about making my trainer look neat when the setting they're in is underwhelming and the exploration pales compared to the rest of the series. The badge requirement to capture even only slightly higher-leveled Pok?mon in the Wild Area, while understandable to a degree, is really annoying. A number of great moves were just removed entirely, the TM system was divided up between Technical Machines and one-use Technical Records, and they give you really worthless options for some TMs (why would I want to teach multiple things Bullet Seed, for instance?) Finally, from the outset of its reveal, I've always found Dynamaxing to be a creatively lazy gimmick and really underscores what a bother it is that Game Freak is constantly reinventing the wheel with their gimmicks each generation instead of keeping beloved aspects throughout progressive generations.
