Page Authority Vs. Domain Authority

Ever since the Yahoo Site Explorer shut down in 2011, internet marketers have been looking for a backlink analysis tool, which they found in the Moz Open Site Explorer. We've already seen how the trend is already sifting more towards Moz Domain Authority from Google's PageRank. Indeed, most SEO experts now also report on statistics from the Open Site Explorer (OSE), such as Domain Authority, Page Authority etc. So what are these metrics anyway, and what do they signify? More importantly, why should you start using OSE if you don't use it already? Let's take a closer look.

Open Site Explorer

Open Site Explorer (OSE) is a search engine that crawls, indexes, and keeps track of the backlinks to every website. It has trillions of URLs in its index, and each update aims at not only improving the speed and efficiency of the algorithm, but also to retain higher quality backlinks in the index while at the same time eliminating the lowest quality links, so that the index can be kept manageable as well as valuable at the same time.
OSE can be used to evaluate backlink data for upto four websites at the same time. For any single site, you can check the following metrics

• Domain Authority
• Page Authority
• Linking Root Domains
• Total Links
• Facebook Shares
• Facebook Likes
• Tweets
• +1s

(Note: You can check the link metrics for free on OSE. But for the social metrics, you have to become a Moz member)
One thing I like about OSE is that, for every backlink, you get to see the exact location of that link, and the title and Anchor text of that link. It will also tell you when a backlink is a nofollow link. That way, you can see where your links are coming from, where to get broken links or links without anchor text corrected, and so on. Furthermore, you can also see the Page Authority and Domain Authority for each of the incoming links to your site, so you can analyse trends and rate your most important backlinks.
Page Authority vs Domain Authority
Page Authority and Domain Authority are two of the most important metrics reported by the Open Site Explorer. Both are measured on a logarithmic scale of 0-100, which means that it'll be easier to go from 10 to 20, than to go from 80 to 90. These metrics are updated once or twice every month, a lot of SEO experts are using these metrics in their reports.
Domain Authority is a measure of how well a whole website will perform in search results. It is the probability of how well any arbitrarily picked webpage from a site will rank in SERPs. It is calculated based on a number of metrics, such as total links, linking root domains, MozTrust and MozRank etc, among other 40 signals. Although it can be used to monitor the strength of your site over time, a better usage would be to compare your site with other competitors, since OSE gets updated so frequently, and Moz takes more than 40 signals into account while computing the Domain Authority. So a score of 40 today isn't the same as a score of 40 an year ago, or an year from now - it changes!
Page Authority, on the other hand, measures the strength of an individual webpage. It is also calculated on the basis of MozRank and MozTrust, since they vary from page to page as well. The DA stays the same throughout the website (like Google PageRank), whereas the PA for each page varies.
So, what do you think about thee metrics? Do you employ them when evaluating your site? Or do you still prefer Google PageRank and Alexa Rank over them? Leave your responses in the comments section below. Cheers :)