A quick Google search revealed this:
"East Penn makes a lot of conventional, calcium AGM batteries. At Auto Zone, the DuraLast Platinum is a calcium AGM, while the DuraLast Gold is a flooded, maintenance-free battery. At NAPA, the Legend is a calcium AGM. At O’Reilly, the Super Start Platinum is a calcium AGM."
The article from which the text is quoted has a great discussion of the different types of AGM batteries and their application to police vehicle use. It also explains the differences between "thick plate calcium AGM batteries" such as the offerings by East Penn, and "thin plate pure lead AGM's" which include Northstar, Odyssey and Optima. The article concludes:
"Both the calcium AGM and the pure lead AGM crank longer and are more tolerant of deep cycle drains than OE maintenance-free batteries. That said, there is a performance difference among these two types of AGM battery. Since the thinner plates in the pure lead AGM have more surface area contact than the thicker plates in the calcium AGM, they are more efficient during both discharging and recharging. The calcium AGM is 'better' while the pure lead AGM is 'best.'"
See:
http://www.hendonpub.com/law_and_order/articles/2015/04/agm_battery_technology
It appears from the article that in the hierarchy of AGM's the Napa Legend is better than a flooded lead acid battery but not in the same category as a pure lead AGM battery such as Northstar, Odyssey and Optima. It also explains the substantial price difference between the East Penn offerings and those of the other AGM manufacturers.