I cross-reference for some, but for the last 2 years I mostly go by Google. Throughout experience, I found that most of my clients and my client's client's use mostly Google, although lately I've seen increase in Bing. It is always useful to consider who the end-user of the website is; if it is mostly gamers or sudens on MAC, it would be one result, if it mostly business professionals within medical field using PCs, it would be something else to consider.