Believe it or not, there is no such thing as the “best lighting.” The lighting you choose should always support the mood and purpose of your image. Neither natural light nor studio lighting is “better.” Neither soft light nor hard light, or broad light or short light are inherently “superior.”
If the mood is meant to be ethereal and dream-like, you wouldn’t want to use an image with hard light and a lot of shadows. Instead, selecting more high key lighting and a softer light source will likely better communicate the goals of your image.
When it comes to fashion photography, you have control of every element in the frame. You control the lighting, the pose, the background, the colors, the clothing… you name it, it’s up to you.
If there is a wrinkle in the clothing, fix it. If the hair is falling the wrong way, make a change. You have to pay careful attention to details and only show what is important to communicate your idea. People see your results, not your excuses.
If there is something distracting in your background you must remove it, recompose, or choose a wider aperture. This is why it is important to have the right gear and knowledge — your tools, paired with your expertise, give you control to express your ideas. Nothing should be “by accident.”