This video shows the differences in the Vampire fight between Gaia Gensouki (JP) and Illusion of Gaia (USA) for the SNES.

Details are on TCRF:

• You have 240 seconds to complete the fight in Gaia Gensouki. Illusion of Gaia reduces this by almost half, down to 140 seconds.
• In Gaia Gensouki, the vampires move slower and their attacks are more varied, but easier to avoid.
• All of the female vampiress' attacks do 2 damage instead of 1 in Illusion of Gaia.
• In Gaia Gensouki, the male vampire drops skull-shaped bombs that leave trailing explosions, and he has a spiraling orb pattern when attacked.
• When the male vampire is alone in Gaia Gensouki, he will shoot three small homing orbs.
• In Gaia Gensouki, the female vampiress causes spikes to appear, which obstruct your path and can be destroyed, and while she has the same rotating orb pattern when attacked, the orbs are much smaller.
• When the female vampiress is alone in Gaia Gensouki, she shoots 8 small fireballs in each cardinal and intercardinal direction.
• Their combined attack is also different: in Gaia Gensouki, they shoot a wide slow-moving vertical beam, while in Illusion of Gaia, they shoot a large, fast-moving ball that heads towards the player.