There's no comparison. Scout has it in a landslide.
Rivals sometimes has better video and photos, but that's a minor thing, and becoming less important with the emergence of scoutingohio, youtube, etc.
Scout has the best insiders by a mile. They also have a very good staff of reporters.
Bucknuts has a great set of reporters too, but their site is a barren wasteland when it comes to recruiting Intel, inside info and other juicy nuggets. They made a big mistake splitting off from scout.
Rivals has a very minor football presence. They do a good job, but just don't have the inside info of scout, or the team of reporters from the other two. Good reporters though, and great bball coverage.
All three sites have good guys and articles, but the thing you pay for in my opinion is the original content. I can find out about a press conference or recruit's favorites on any site. I can't find out about stories out of closed practices or recruiting secrets at other sites like I can at Buckeye sports bulletin. Nevada and bill set themselves apart.