I think it depends on ones experience, workflow and context.
When I started I used inline styles and inline script (and horrible markup) and while I was learning it was good to see the fruits of my efforts. As I got better [sic] I became annoyed at how difficult and time consuming it was to change things. I then began using
<script> tags. After repeating the same things in many files, I learned the advantages of external files.
<style> to the DOM.