Here's a rundown of the differences between CV64 and LoD's Reinhardt/Carrie quests. It would be up to the player to decide if it's 'worth it':
1. The intro is different. CV64 has the Castle with Thunder, followed by Malus playing the violin. LoD has the running maiden getting kidnapped and sacrificed to bring the ghost of Dracula back.
2. Reinhardt and Carrie actually have one line of voiceacting at the start of the game. Reinhardt says "Courage... don't leave me!" and Carrie says "No matter how it gets, I have no regrets" (I think).
3. The first stage in CV64 is the Forest of Silence, and this stage has a reference to X68000 with the thunder striking the tree right before you (this can actually hurt you). These scene is not in LoD, and LoD has the Foggy Lake as its first stage.
4. There's a cutscene with a bleached white skeleton that Reinhardt examines (almost in a Resident Evil/Silent Hill style), then a cutscene wtih skeletons rising out of the ground. This scene is not in LoD at all.
5. The entire layout of the Forest of Silence is different except for the battle vs. the Giant Ape Skeleton.
6. The music for the Castle Wall "WatchTower" has a different set of instruments. The CV64 version uses Chorus (which sounds great), the LoD version uses Strings and has a little piano melody in there as well. Personally, I miss the CV64 version.
7. I don't think Dracula has voiceacting lines in LoD, but he does in CV64 "Miserable worm, upstart weakling. All those who oppose the Dark Lord... must die."
8. As mentioned before, the four towers have undergone some changes, some minor, and some significant. The tower of science, the tower of sorcery, the tower of duels, and the tower of execution, all have changed layouts. The most predominant of changes is in the Tower of Execution, where the center section on the molten steel (lava?) is upright with bridges in CV64, but it's completely broken down and tilted in LoD.
9. You actually go on the clock face and hands in LoD. In CV64 you just go through a door and you're at the Keep.
I think I missed a few, but that's the stuff I remember changed the most.