I was confused about this as well. I hope there's some official news on the differences and what triggers them exactly. I remembered them stating it was purely related to 1.0 characters, but perhaps there's more to this. : /
I'm a Legacy player. The intro I got was the same as the new character I made during beta. I watched the end to an era trailer (the one with Bahamut blowing stuff up and the Warriors of Light coming from their time travel episode) and saw my character encounter the masked mage in limbo area.