Its sort of like when Super Mario Bros. made its way to the SNES.
However, this one is better and has some additional game play.
My ratings by category
Sound: C (Music = D & SFX = B)
Graphics: A
Game play: C+
Game Design: B+
Overall Satisfaction: B
The sound effects are much better and crisp, but IMO the music although smoother isn't that great as on the GBA. I think the GBA version had more suspense and mood. And there's no option to adjust music and/or SFX.
The graphics are definitely much sharper.
For DS game play its the typical pic and that's it. So that's another disappointment, but although you might not 100%, you do get used to it.
But the game design is nice. While there isn't a ton of additional sequences, and they're not spread out, there are additional scenes. Mainly just early in the game (where you'll control Nico twice). So if you are just looking to get this game because of deleted sequences maybe you should rent it first, especially since a lot of the sequences are towards the start.
Other sequences include you solving puzzles. Mainly, when you had to work something out on the GBA version (like the church's spyglass lens) there's a puzzle in its place.
But overall, if you enjoyed the GBA version, I'd recommend picking up the DS version even renting it first if you're so hesitant. Because overall, it isn't a disappointment.