The Arch wiki is fantastic. I've not heard an explanation as to why it is so much better than Ubuntu/Redhat. A community of tinkerers? Lack of hegemonic domination from Redhat/Canonical?
Probably because it's generic enough to be applicable to the broader Unix ecosystem. I refer to the Arch Wiki all the time even though my Linuxen are almost exclusively either Slackware or openSUSE.
The downside, though, is that some distros have specific tooling for solving a problem, and that tooling is often more appropriate than the information in the Arch Wiki (though the AW still helps if you want to understand what those tools are doing and why).
