What is dif between sonic adventure and sonic adventure dx?

SA is for the Dreamcast, while SADX is for the GameCube.

SADX has the 12 Sonic Game Gear games as unlockables.

SADX has 60 missions in it.

SADX has a black market in the Chao Garden.

SADX allows you to put your chao in the Tiny Chao Garden.

SADX awards you for collecting all 130 emblems.

SADX has Cream cameos.

There are more.