Not to be a curmudgeon, but after reading the entire link, there are many mis- statements and confusing details listed.
DO NOT CONFUSE 'gel' and 'maintenance free' batteries with true AGM batteries. THEY ARE NOT THE SAME! True 'gel' batteries are still being made and are much more temperamental that a true AGM battery, while many 'maintenance free' batteries are simply valve-regulated liquid cell batteries that are primarily used in engine starting applications.
This goes for construction, ratings, use and especially charging set points. If you charge a Lifeline AGM at the voltages listed in the long......you will damage them!!!
DO NOT USE CCA RATINGS as a measure of a true deep cycle battery's capacity. You need to compare the '20 hour rate' across all of the batteries that you are considering.
always check with the manufacture of the batteries you are using for the specific information required for proper battery charging voltages and corresponding state of charge levels.