I believe that the signature edition is the collectors edition when you pre-ordered the regular one it automatically upgrades you to the signature edition. I haven't heard any other editions. hope that answer you questioned.
the uk got the animus edition. which comes with the assassin's creed encyclopedia. why do they always get the best one's I just saw that the uk with have the final fantasy crystal edition. If they get a better mass effect edition (haven't check yet) I will
just be sad.
The collector's edition from GameStop you get a DeVinci's Flying Machine collectible with an Ezio that can fit onto/into it as well as the Signature Edition of the game. Cannot wait for Midnight tonight!