To answer your question, content is important for both, different content is more important for one than the other and visa versa!
Content is still king, but only if your SEO is correct. Shitty HTML hurts bad, even more than a slow site.
For SEO quality, well written content, is more important in mainstream than adult. Who reads anything on adult site? Just the Search Engines.
For SEO quantity of content is more important in adult than mainstream. The search engines know what your site is about with the few words you have written and the abundance of image and video titles, alternative text and caption. Even comments.
Both need pages with good titles and descriptions for the SERPs, so people click. Either good meta tags or great headers, sub headers and intro paragraphs to appease the SE robots.
Image and video searches are becoming more important for both. File title/name, alternative text and caption for images and videos is very import for both, more important for adult.
