Getting $500$ backlinks from $400$ different websites is better for ranking purposes than getting $500$ backlinks from $40$ different websites because the links from $400$ different websites will generate more traffic, and traffic is the most important ranking determinant if we get too many links from the same website, the search engines automatically assume we are buying those links search engines consider link diversity a sign of independent endorsements of a website's content the links come from $400$ different websites, those links are more likely to generate social sharing