If you are choosing between the original Sun/Moon and the Ultra versions, Ultra Sun offers a significantly expanded experience: Pokémon Ultra Sun (3DS) Review - CGMagazine
If by "high quality" you mean better gameplay, several "enhanced" versions of Ultra Sun exist that fix difficulty and Pokémon availability: HELP WANTED FOR POKEMON ULTRA SUN : r/PokeMoonSun pokemon ultra sun decrypted high quality
: Running the game at 4x or higher resolution (e.g., on devices like the Ayn Thor Max ) makes cutscenes and gameplay look significantly sharper. If you are choosing between the original Sun/Moon