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SEO Keith has pretty much hit it spot on. I would try and use a combination of all 4 if at all possible. From my observation GWT accuracy seems to vary dependent on how often your content is crawled..... showing a history of all your links i'm not sure it can be beaten. But accuracy of what is included I am unsure. We have a few external links that were pointing at our site which we know no longer exist. 3 months on they are still in our link profile according to GWT.