You need the Peukert Exponent value based on the brand and model of the battery. A lower number is better. A good AGM will have a low number (slightly more than 1.0).
The bigger issue is your
alternator regulator needs to be set up for AGM too. Screwing up the
charging profiles will really trash an AGM battery fast. Not having the
alternator regulation right to would be costly. The Freedom is fine for
shore power charging even if not perfection. These days AGM's cost too much to screw that up. Done properly the lower internal resistance will allow a faster charge from the alternator. The Freedom is faster too but when docked and plugged in - who cares? The "potential" AGM payout is fewer
engine hours to recharge the battery because the alternator can
work at a higher amp rate longer. The low
maintenance is also a bump for you too.
The common problem with AGM is poor charging. They really won't tolerate it.