USUM is really unimpressive for an enchanced version
Honestly, story aside, , I think it's one of the better third versions in terms of addition/changes of content.
- Sidequests in a pokemon game. Reallly adds life to the region.
- Way more pokemon in the overworld, you can spot many like Murkrow, Bewear, Magmar, Wingull and more hanging out in certain areas, and you can play with other people's pokemon too. Makes the USUM version of Alola feel much better.
- regional alola pokedex expanded by 100 pokemon to include much more choice.
- roto lotto (basically the return of O-powers)
- Postgame is much better with Battle Agency, Rainbow Rocket, and Ultra Warp Ride added on.
- The ability to own totem sized pokemon yourself.
- encountering ultra beasts in their own environment. Finding Guzzlord eating a city instead of just on a random route was so much better.
- a lot of smaller improvements, like SOS battles being a lot less annoying, being able to get vikavolt earlier in the game, etc
Among a lot more.
Unfortunately the story was royally fucked up. The entire Lusamine family had their intentions so muddled, ultra recon squad sucks ass, rotom dex is way more annoying, and the final battle with Hau isnt nearly as impactful as battling Kukui in vanilla SM.
I still give US/UM the edge as the better game, but it's a bummer that it failed to be the "definitive edition". It was just SM, better in some aspects, worse in others. Which makes it probably the worst third version to me, even though I feel it added more than Emerald added to Ruby/Sapphire.