they both have the same story line
only some items are diffrent
in darkness you have the violent seed which raises your attack and special attack
in time you have another seed which reduces attack and special attack
Also you have the
Foe-Seal orb that makes all enemy's in the room in paused modes
And the Foe-Hold orb makes all enemy's on the floor petrified and kant do moves.
i got darknes a while now ;)
gah i wish i had time D: mewtwo is on 2 dungeons D: Ageis cave (only darkness) and dark crater :/
the celebii in the story line is so cute (its shiny)in darkness you get Mewtwo in time you get Celebi so your choice