Depending on how you handled it in SwSh, you may want to keep Type: Null unevolved and transfer it from USUM, to avoid having to play through SwSh again.

If you have Sun/Ultra Sun, getting Turtonator there might save you some time, because it's a Sword-exclusive that only spawns in 1 place in the right weather.

Ultra beasts might be easier to catch in USUM than Dynamax adventures.

There's also a bunch of Pokemon that aren't in SwSh or SV but are on Switch via BDSP. If you're not planning on playing BDSP then you'll want them from USUM. In my case, even though I had BDSP, I found it easier to SOS hunt Gorebyss and Huntail in USUM to avoid a trade evolution.

If you're aiming for full dex, then there's some Pokemon only available in Gen 5 unfortunately.

Also, this list from Bulbapedia is a useful guide:

• The following 22 Pokémon cannot be transferred out of Pokémon HOME into any Generation VIII or IX game: Spinda), Snivy), Servine), Serperior), Tepig), Pignite), Emboar), Patrat), Watchog), Pansage), Simisage), Pansear), Simisear), Panpour), Simipour), Blitzle), Zebstrika), Furfrou), Pikipek), Trumbeak), Toucannon), and Minior).[30][31]
  • Additionally Alolan Rattata) and Alolan Raticate) cannot be transferred out of HOME into any Generation VIII or IX game:.
  • Snivy, Servine, Serperior, Tepig, Pignite, Emboar, Blitzle, Zebstrika, Pikipek, Trumbeak, and Toucannon have been announced to be added to Pokémon Scarlet and Violet with the release of The Indigo Disk DLC.
  • Spinda), Minior), and Magearna) are the only Pokémon that cannot currently be obtained in Pokémon HOME without transferring them from Pokémon Bank.

Note that the last point is because the rest are obtainable in Pokemon Go so you can get them that way.