Princess Sailor Moon's uniform is considerably more elaborate than Sailor Moon's.
Unique to the live-action series, Princess Sailor Moon is a powerful combination of Sailor Moon and Princess Serenity, introduced when Usagi is "possessed" by the spirit of her former self. She originally appears after Queen Beryl takes the Shitennou hostage in exchange for Mamoru. Silently furious, Sailor Moon transforms into Princess Sailor Moon and halts Queen Beryl using her sword.
It is obvious that Princess Sailor Moon is not the same as Usagi when she shows no remorse for the fate of the Shitennou (at least Nephrite's fate), and when she refers to Mamoru as "Endymion" rather than using his civilian name. She is also constantly angry, and tends to leave flaming carnage in her wake. In one Act, Usagi's friend Naru accidentally gets too close and winds up in the hospital for a while. Though smiling in most promotional material for the series, Princess Sailor Moon does not smile in the series itself until the very end.
Princess Sailor Moon states to Usagi during inner dialogue that she has no qualms about destroying the Earth if Endymion is ever taken from her, and later on even summons her own special minions to fight her friends, all bearing moon-shaped signs similar to hers. Usagi struggles to suppress her power in fear that she would eventually destroy the world, something that comes to light in an Space Runaway Ideon-like fashion for the series finale. Her internal conflict is the major conflict for the rest of the series.
Princess Sailor Moon has a sword, which also doubles as a harp with invisible strings. She plays this in sorrow while thinking of her lost prince, and is capable of using it to heal people and the land. Other than this, the exact effect of playing the harp is unclear, but much of the time it causes the power of her Silver Crystal to feed the power of Queen Metaria, accelerating the devastation of the planet. Using the sword in its capacity as a weapon, Princess Sailor Moon can deflect enemy attacks and can unleash devastating projectile attacks. She also has the ability to levitate and to teleport.
Like other characters unique to the live-action series, Princess Sailor Moon's outfit was designed by Naoko Takeuchi herself. Her sailor outfit was considerably more elaborate than Sailor Moon's, and included pearls on her gloves and lace on her skirt.