I went with both, since there is an Xbox version of DA which tells the story better than the 360 version, even though it 'forces' you into some situations where you have no choice but to KO/Kill (the train mission especially).
That said, I also liked the D.A. 360 version for the graphics and challenges it afforded, but I hated the storyline and lack of cutscenes/dialogs.
i had chaos theory and double agent on ps2 and they were both good. but i can't say to the 360 version since i tried it on my pc but it slowed down so frequantly i could hardly get the gamelay experience of the next gen sam fisher