Two main ones I know of are the steel speaker panel that includes a decal versus the black wooden speaker panel that came with the original Luci. Someone can correct me here but I think the other difference is in the window for the lower playfield, I believe the vault Luci has a 'better' one that is easier to remove.
Luci is certainly on my list to own and I'd take the Vault over the original if the price is the same and if condition were identical in both cases I'd pay a little more for a Vault too.