It's a very tough decision between the two, but I have to go with style. Content is great, but good content written uninterestingly is just plain boring. A good writer can make even dry material seem interesting. Particularly in fiction, I would rather read great prose about shallow characters in a silly plot than stale, stilted prose about interesting people doing something epic. My opinion of J.R.R. Tolkein, for example, is that he created fantastic ideas but it's clear from his prose style that the man was a linguist first and a creative writer second. "The Lord of the Rings" is an awesome story, but you can't tell me that it wouldn't have sounded better committed to paper by Robert E. Howard, or Michael Moorcock, or even Philip K. Dick. I know I'm committing high blasphemy by citing this example, but I think the fan worhsip of Tolkein is a perfect example of the difference between style and content. Tolkein is all content.