Famitsu Xbox talked to Devil May Cry 4 producer Hiroyuki Kobayashi about several topics including the game going to Xbox 360 and differences between versions.
The reason for the game going muti-platform is because “[the game] is an extremely strong name overseas,”. As for difficulty “The game engine is shared,” so porting is easier than with last gen systems. Kobayashi did note that the 360 version “still [has] a ways to go” and was just started after the announcement.
There will be no differences between versions and content will be the same. A new playable demo will be at this year Tokyo Game Show.[Source]