Scarlett is the main character in Gone With the Wind, and its natural to see parallels between her and the author, Margaret Mitchell. Like Scarlett, Mitchell broke down barriers for women in the professions (Mitchell as a journalist, Scarlett as a mill owner). And like Scarlett, Mitchell married more than once, and those marriages were not all happy (Mitchell's first husband was an alcoholic).
But in some ways, Mitchell is less like Scarlett than she is like Ashley Wilkes. Scarlett, after all, hates to read, and knows just about nothing about current events or literature. It's Ashley who is cultured; Ashley who cares about writing and art; Ashley who, like Mitchell, is educated and thoughtful.
There are numerous scenes in the novel where Ashley tries to explain philosophy or history or what is happening in the South to Scarlett, and she always furrows her brow and just gets more confused (see 31.88-93, for example). In these scenes, Ashley becomes the voice of Margaret Mitchell, trying to explain the themes of the novel to the main character, who is hopelessly at sea.
So does that mean that Mitchell likes Ashley more than Scarlett? Well, no, not really. It's true that the novel often condemns Scarlett for the very traits that seem to come from Mitchell—her drive, her stick-to-itiveness, her supposedly unwomanly ambition (you don't write a best-selling novel the way Mitchell did without having a ton of ambition).
But the novel also condemns Ashley—and again for the very traits which seem to link him to his author. Gerald early on calls Ashley "queer" (2.104) because he's interested in art and poetry and culture, and that's not just a description, but a condemnation of unmanliness. Ashley is often referred to as a dreamer—and because he's a dreamer he's "as helpless as a turtle on his back" (40.102). Not exactly a vote of confidence for dreams.
Ashley is useless—and he's useless precisely because he's the one person in the novel who could have written the novel. When Ashley says, "I do not know what the future will bring, but it cannot be as beautiful or as satisfying as the past" (11.16), his vision of a beautiful Confederate past, and his eagerness to dwell there, is also Mitchell's vision and eagerness. She's written a whole book to create the vision of a beautiful, satisfying past. But whereas Mitchell's vision brought her fame and fortune, Ashley's makes him barely fit to live.
Which just goes to show, if you have a choice, it's better to be a writer than a character. As for whether it's better to be Ashley or Rhett, well, we'll leave that one up to you.