Disgaea is also enhanced and cheaper on PSP/DS than on PS2, but I'd go with DDS.
edit: I'm pretty sure at least most of those are also cheaper than $30 on amazon.
You're probably right, but i'm not a fan of buying online. I should though, I guess i'd save money on the long run.
Edit : After checking reviews/videos, i'm most interested in either Disgaea HoD or Nocturne/Digital Devil Saga. The others doesn't really seem to fit my taste.