The best Buffy

Well, by the time the show hit the air Swanson had aged out of the role anyways. I don't think she was terrible in the movie. The movie had many failures, but she wasn't one of them. In fact, I don't think that much of SMG. She had some fantastic moments on 'Buffy', probably should have gotten a few Emmys nods, but she also had some clunky moments as well where the show asked her to reach beyond her limits. I have no idea how Swanson would have done in the role, but I'm not so quick to dismiss her.

You're right in that I could not say what Kristy Swanson had that SMG did not. Make my Buffy SMG. For me, the difference in their portrayals is that SMG's Buffy was more poignant. She communicated the angst of a young woman whose life is not under her control and more importantly, knows she will die young. Kirsty Swanson seemed like she was having a big adventure. I prefer the former.

However, it is worth noting that there is a subtext to the relationship between Buffy and The Master in the film that never gets explained or explored. I've always believed it got cut from the script. This plot element might have given Swanson something more to work with.