Atm it works just the other way around actually. Sam can't be hit while dashing, but when ghosts dash they are very dangerous! This makes dashing a tool in one case but forces you to use it carefully as the movement of the ghosts also becomes more unpredictable.
I'm not sure yet if the invulnerability will stay though. Might make Sam the 'right' choice over Sara, and I want them to be both viable.