When talking to clients about link building, one of the first things I bring up is why Yahoo Site Explorer and Google Webmaster Tools are the best sources for comprehensive backlink data.
I go on to explain how Google purposely offers random and incomplete data when you run a link: command on their search engine. I also explain how MSN's link: command turns on and off as if it where controlled by The Clapper (dating myself a bit with that reference, I know).
I then go on to explain that the link: command in Yahoo, which automatically sends you into their Yahoo Site Explorer section, delivers a very comprehensive set of backlink data that can be sorted and filtered in a variety of ways. Google Webmaster Tools offers a similar level of detail, but the data is organized in a slightly different manner; it actually lists every URL that has inbound links pointing to it, and includes the actual number per URL.
Note: Just in case you didn't know, in order to access this backlink data, you must first register your site with Google Webmaster Tools and then submit and verify an XML sitemap. Once you've completed that process, Google delivers a wide array of information including this detailed backlink data I'm referring to.
So client education aside, what's the absolute best tool for conducting research into the backlink portfolio of your site? Should you go with Google Webmaster Tools or Yahoo Site Explorer?
Let's start by comparing the numbers.
I checked a number of sites that I have access to via Google Webmaster Tools, and compared the backlink data. Interestingly enough, Yahoo Site Explorer reported more backlinks than Google Webmaster Tools for every domain I checked.
Incidentally, in order to compare these numbers, I filtered the Yahoo data by choosing to view "inlinks" (that's Yahoo's term for inbound links/backlinks) and choosing the "Except from this domain" drop-down option as well as the "Entire Site" drop-down option.
So it would appear that at Yahoo Site Explorer has the upper hand, but as with most things in life, quantity does not necessarily equal quality.
The next thing I chose to analyze was the usefulness of the data being presented, or better yet, the usefulness of how the data is presented.
On the surface, it would appear that Google Webmaster Tools has the upper hand in that they deliver detailed backlink data organized by URL, allowing you to easily identify what pages of your site possess the most backlinks as well as exactly where those links are coming from. Yahoo's data is delivered in the form of a search result, simply listing the actual backlinks pointing to either the homepage or the entire site.
But as my favorite college football pundit, Lee Corso, likes to say, "not so fast my friend." Thought it is difficult to prove this empirically, it appears as if Yahoo Site Explorer lists the backlinks in order of their potency. In other words, the most powerful links are listed first.
If you don't believe me, check it out on your own sites (and don't just base it on the PageRank assigned).
Anyhow, back to the task at hand. Admittedly, there are various other factors to consider when evaluating these two backlink analysis tools, but I'm writing a blog post, not a thesis. I'll definitely follow up on this topic, but for the time being, I think I've come to a conclusion.
If you're analyzing the backlink portfolio of your own site(s) both Google Webmaster Tools and Yahoo Site Explorer offer uniquely valuable insights. So in this respect, it's a tie.
However, if you're looking for competitive insight, it's a no-brainer. Google Webmaster Tools limits you to just your own site, but you can analyze any site under sun in Yahoo Site Explorer. So if you're looking to see what you're competitors are doing (and you definitely should be doing that) it's all about the big Y!
Bonus Fun: In Yahoo Site Explorer, you can actually run a backlink query for both www.yahoo.com and www.google.com. Let's just say that their backlink portfolio is a bit humbling.