It had a more serious anime style. And didnt let it affect the mood and tone of the game. It felt very cheap 90's anime- but GOOD cheap 90's anime. It was still dark in tone, and used the style to explain it's few animated cutscenes.
PoR is just cartoony. Saturday morning kids Anime cartoony. That CG/anime opening was just odd too. And it doesnt help that it's yet ANOTHER metroidvania, with all the old Rondo sprites, and a failed attempt at a Bloodlines sequel with an even worse plot and the loosest of connections to it's source. DoS is where things started to go a little south, but DoS still had good gameplay at least, since it was really just Aria 2.0. PoR is where the formula just got stale, and IGA's obsession with gimmick driven gameplay and "gameplay first story second" really shone through the worst.
Rondo was just your classic point A to B Belmont vs Dracula plot, with the added twists of animated cutscenes adding a bigger sense of narrative to the game, and alternate pathways and shortcuts, making the overall map feel much bigger and secret laden than previous games. It also was the first "new" game to have a redbook audio soundtrack, after Chronicles, which was just a CV1 remake.