Well, a feeling of continuity for one. I know someone said that any quest based abilities, etc (such as the blood pool) that you gain will be re-added (or an equivalent of it) as you re-accquire your soul bits. Also greater control over choices that you make that might affect things in PoE2, though there probably won't be many of those.
I don't think we know all of the benefits of importing a save yet, but the primary draw is likely that feeling of continuity.
From the Q&As i got the impression that, no, the is no "benefit" to importing the save, unless you really want to continue THE choices and THE character. When starting new game you will be able to define the game state and there is no info about additional benefits. It doesn't seem like you are encouraged to prepare a save for a sequel, rather that you can continue or start a new character and it should be both equally good.
I made 2 or 3 wrong decision in a character playthrough, if there is no differen or benefit then I will not play same character again just for "perfect state"