[Grammar] before you leave/before you've left

[englishhobby]

Are both variants correct and natural? If yes, what's the differentce?

1) Come and say goodbye tomorrow before you leave.
2) Come and say goodbye tomorrow before you've left.

 

[emsr2d2]

If yes, what's the [STRIKE]differentce[/STRIKE] difference?

Note the correct spelling of "difference".