Dracula X is based on the PC Engine CD / TurboGrafx-16 game Rondo of Blood. Rondo was exclusive to Japan until the PSP, and instead of porting Rondo to the SNES and localizing it back in the day, Capcom made Dracula X more of a reimagining. They're basically two different games.
Dracula X has:
I should probably clarify I've never played either game; I'm just saying what I've read on the wiki and what I've seen others say. That said, while Rondo is definitely more popular, I've seen some people say that Dracula X is still a good game.
- a similar, though slightly altered, story
- redesigned or entirely different levels (also there are fewer of them, and they're more linear than the ones in Rondo)
- one playable character, as opposed to the two in Rondo
- rearranged boss orders (additionally, some bosses were replaced with new ones or removed entirely)
- an updated/different soundtrack
The soundtrack isn't really different. There are less songs in Dracula X cause there are less stages but every track in Dracula X is based off of one of the tracks in Rondo of Blood.
Honestly I think they did an amazing job converting Redbook audio to SNES.
It's a fine game. I feel like the difficulty gets a bit too cheap towards the end (there are bottomless pits everywhere) though.