The content is, of course, the dialogue and the characters.
The style we could see as being the look and feel of the final film. But I think that's wrong and too narrow a view. The style is the structure and pace of the script.
Many scriptwriters would argue that content is more important than style. "Let's get the content down first then add the style later" or even see the style as the director's 'bag'. It is an often used criticism that someone has 'put style over content'. And it is true that this can lead to an empty film. But content over style is also a danger.
So you need style and content, yes.
Style over content, no.
Style before content, yes.
That's what may be a challenge to some people. Before dialogue, before structure, even before story - comes style.
Only when we understand the style of the film, how it will look at the end, can we write the best script. To do this effectively would mean often breaking the traditional work structure.
Plus how we fit that idea of style into a 12pt courier script. That's the task.