I actually prefer w3 schools to MDN. If I accidentally click on an MDN link it confuses me for a few seconds before I realize what happened and navigate back to w3.
By extension - the best SEO guide is almost certainly the first listing for 'SEO guide' on google.
Only if you can assume that they followed their own guide. I could see an SEO company posting a fake guide to make their own techniques more effective relative to any competition using that guide.
