The Deluxe Edition is the definitive version of the game, including content previously released as DLC: :

Under Defeat HD: Deluxe Edition is a high-definition remaster of G.rev’s classic arcade and Dreamcast shoot ‘em up (shmup). Set in an alternate World War II, players pilot a heavily armed helicopter through intense battles between the "Empire" and the "Union".

For users on modded Xbox 360 consoles, this edition is typically handled as follows: Transfer Games to Xbox 360 via USB | PDF - Scribd

: A 16:9 widescreen adaptation with refined HD artwork and textures.