Saleswise, I think the FFXIII thing is a bigger deal. DQ9 will probably sell more, but most of the fans of the PS2 games last generation have a DS now, especially in Japan. If they don't, it's relatively cheap and I don't see it becoming a huge deal for most.
Meanwhile, many people have been using FFXIII as justification in spending at least $400 on a PS3. Many of those people (an unknown, but sizable, amount) will realize that they can now get the same game on a different system for $280. Now, many will still prefer it on Playstation, or one disc, the lead platform, yadayadayada, but it will greatly impact sales.







