Dimitri is just an undeveloped jerk! Her lies to Anastasia, constantly fights with her, starts to fall in love with her just because she changes her hair and wears a pretty dress, and only decides to care about Anya being reunited with her grandmother when he finds out she's the real Anastasia. Derek, despite at the beginning he constantly fought with Odette and fell for her for her looks, does develop as a character. He could have been more well-developed, but he's pretty developed. He learns that he needed to be able to express the way he feels about Odette, otherwise he'd lose her. He ended up causing her death because he still wasn't able to express his feelings other than for her looks and he regretted not being able to tell her how he really felt until it was too late. He doesn't lie and just has a hard time expressing how he feels.

Derek may be shallow at first and a little oblivious, but I got tired quickly of Dimitri's conman-ness.

^^what both of you said.

Both are self-centered and shallow, but at least I don't find Dimitri as bland and stupid as Derek is.

By far. He is shallow but he is really benevolent and charmingly romantic.
Dimitri is probably more amoral than Merida, Flynn and Tulio together.