This page on the Pokemon Ultra Sun and Ultra Moon Wiki Guide lists every difference between Ultra Sun and Ultra Moon, from exclusive Pokemon, to time differences, and more.

EditExclusive Pokemon

As it is with all other Pokemon titles, certain Pokemon will only appear in one version of the game and not the other.

EditExclusive Legendary Pokemon

All Legendary Pokemon (not Mythical!) are catchable in Pokemon Ultra Sun and Ultra Moon. However, some are only catchable in one version. These will be obtainable through Ultra Wormholes.

EditPokemon Ultra Sun Legendary Exclusives

EditPokemon Ultra Moon Legendary Exclusives

EditExlcusive Totem Sized Pokemon

Totem Pokemon are returning to Pokemon Ultra Sun and Ultra Moon, but this time, you’ll be able to add a few to your collection after finding special Totem Stickers. Here are the exclusives we know of so far.

Ultra Sun Exclusive		Ultra Moon Exclusive
Totem Sized Lurantis		Totem Sized Salazzle