For me, Dawn of Sorrow has better bosses on the whole, and a much better extra mode, but aside from those features, I can't think of anything I liked better at all. Heck, I even think the graphics of Aria of Sorrow look considerably nicer. Collectively, the environments are simply more interesting in concept and execution. I guess that's all beside the point, given the topic, but unfortunately, that game didn't have any saving grace for me. I even think Curse of Darkness and Lament of Innocence have great to excellent soundtracks, nice cut scenes, and intriguing characters, despite them basically sucking, in my opinion, but with DoS, it's like one bad thing piled on top of another without enough good to make me think any remotely fond thoughts about it . . . likewise with Portrait of Ruin, for whatever that's worth.
Well, I didn't like Aria of Sorrow that much. I can't really put my finger on it, but I felt Dawn improved just about everything (except the story, artwork and music. Which may sound like a whole lotta things, but I honestly don't think the story is any good in any of the Castlevania games, so it's not such a big deal for me. Also, I know literally nothing about anime so the artstyle didn't bother me either. I noticed it looked a little less "serious" and more japanese, that's all. I definitely prefer Ayami Kojima, but artwork doesn't make or break a game for me.
Now, the one thing I really loved in Aria was the music, so Dawn was kinda disappointing for me in that respect. Throughout the years I've learnt to like the music in DoS though, but it's far from a series hightlight IMO.
Anyway, most people seem to prefer Aria so I can't really argue with that. I just wholeheartedly disagree 100%
As for Curse and Lament... not my cup of tea. Though Curse has excellent music!