This is probably a more interesting metric, which is seeing the referrer lets you know how someone found your site. And Google consistently scores higher numbers here on my personal web site.
However, that statistic says more about ranking too, since sites higher in the ranking in Google's results will get more referrer hits, if the same site was lower ranked in Bing's index it would get fewer hits from Bing. In the ideal case one could compare the relative referrals from a site which falls in the same spot (preferably #1 for best sampling) on both indexes.
However, that statistic says more about ranking too, since sites higher in the ranking in Google's results will get more referrer hits, if the same site was lower ranked in Bing's index it would get fewer hits from Bing. In the ideal case one could compare the relative referrals from a site which falls in the same spot (preferably #1 for best sampling) on both indexes.