>>150717333
Because one has a defined purpose through her layers of irony by being an audience surrogate character, and the other is somehow representation as the ultimate failure in Ben's creation because she only existed for 45 seconds.
But hey in another timeline Season 1 Rachel gets "character development" and ends up being a fucking nerd that fulfills the same role as Sarah. Maybe somehow that hypothetical is more preferable? I don't know I'm just rather neutral on the both of them.