But Sara wasn't part of the original team either. So if people are technically saying because of the 'original team', take into consideration, Sara came into play in "Cool Change" was not an original member of the show.
*rolls eyes*
I'd say the second episode makes you as big a part of the original team as anything else. By that theory, Brass is part of the original CSI team as well. While that's true, we never actually saw that much of him as the head of CSI.
Sara is a part of the original team. She's in all of the original team cast shots, she showed up in the second episode, and was always supposed to from the wishes of Anthony Zuiker.
Even if she wasn't, second episode makes you part of the original team far more than fifth season would.
And love her or hate her, Sara has always been a part of the dynamic. Sofia never really has. Her appearances have distracted from other things, and now she's not even a prominent part of the show. She's just sort of... there.