Graphics: 9.5/10
Since it was made for the DS and isn't just a GBA port like the others the graphics are smoother and more polished. Evidence is 3D and fully rotatable. There is also a 3D cutscene. Animations have a lot more frames, particularly Klavier doing air guitar. There were a few barely noticeable slowdowns.
Gameplay: 8.5/10
If you played the fifth case in the first game, it's very similar to that. You can dust for fingerprints, identify footprints, recreate crime scenes, and other things. But only at specific times. Which aren't really that often sadly. The main new feature is Perceive which is Apollo's ability to see nervous habits when someone is lying. It takes the place of Psyche Locks from the second and third game. It's kind of annoying because the thing you are looking for is so minute that you will often overlook it. Everything else is pretty much the same.
Sound: 9.5/10
Since it's for DS the sound is much better quality. The only problem is that when characters from the first three games make cameos they have the GBA sound clips. It's only really noticeable when they go, "Objection!" and a new character goes, "Objection!" right after much clearer and louder. Lots of new songs and also a lot of the songs from the original game which makes me happy.
Overall: 8.5/10
There are only four cases, but the fourth case is very long. The new characters are nice but right now they aren't as charming as the original characters. Hopefully in future games they will develop more. The cameos are really great but they only make a difference if you've played the first three games. There were some characters that I really wish made cameos but didn't. I found it really easy to tell who was the culprit right away even if I didn't know all the details. The fourth case really makes everything worth it though. So, overall, not as good as the Phoenix Wright trilogy, but still very good. And it's not really a spoiler to say that Phoenix is in it. If you're a fan of the series you will like it. But as always, play the other ones first.