Metrics tell a portion of the story.
Moz, in my opinion, is slow, does not update often enough, does not have a large enough sample of back links, and does not do most sites justice in their metrics.
Majestics TF and CF is better. In my opinion, best on the market.
Ahrefs is mediocre, but gives a better snap shot than Moz.
The only way to really know what the site is like, is to check the back links yourself. These sites are automation. They never show the whole picture for a domain. Look at the domain yourself and then figure things out.
A site with thousands of blog comments with Chinese and Russian Anchors? Obviously spam.
A site with only contextual exact match anchors? Obviously a SEO had the site and has a reason for letting it go.
You can tell after looking at enough domains what is 'crap' and what is not. I can tell you one thing, having looked at domains and used Majestic / Moz / PR / Ahrefs, a SEO'd site with a penalty can have AMAZING Metrics. A clearly spammed site can have a Moz Spam Score of Zero because Moz has such a small sample size.
Use the metrics to filter domains and then check them yourself. Do not buy a domain because it has 'great' metrics.
