I switched to TWO 6V AGM's 2 years ago and LOVE THEM.
You guys missed a Major differnce in AGM and Normal Lead Acid (unless I over looked it - I was speed reading). The Discharge rate while in storage. I think the AGM's are like 1% per a month and LA are like 1% a week (with zero vampire draws on them).
Advantages of AGM
1. They are spill-proof
Unlike the traditional lead-acid batteries that freely flood their electrodes, AGM batteries have glass mats that prevent this. Additionally, it is the function of these glass mats to avoid spillage. Rather than absorbing the electrolyte, the glass mats work by holding the electrolyte in place, preventing it from spilling over, even when the battery is placed in odd positions.
2. They have a high-power output.
Because of the way that they are designed, the AGM batteries have minimal internal resistance. This, therefore, enables them to provide sufficient bursts of power when necessary, such as when one needs to start a battery. Due to this feature, these batteries respond better to loading than any other battery on the market.
3. They have a short charging time.
AGM batteries, compared to flooded batteries, charge quickly. When compared to flooded batteries of a similar capacity, the charging rate can reach five times faster with the same power source.
4. They have a longer lifespan
AGM batteries have a longer lifespan than traditional flooded batteries. Moreover, not only do they serve for a more extended period when they perform the same tasks, but they also last longer when they are not in active use. This is because self-discharging is minimized in these batteries, unlike other types of batteries, which is a huge problem. This ensures that one does not have to keep charging them after an extended period of inactivity.
5. They are durable.
These AGM batteries were originally designed to serve the aircraft industry. This means that they have a sturdy design, one that can handle conditions of intense vibrations, just like those in military and commercial aircraft. Because of this property, they are a favorite for high-end motorcycle riders and race car drivers. The sandwich construction method adopted in their design ensures that their internal components do not fall apart. Moreover, they are invulnerable to the subsequent wear and tear that may result from frequent and continuous vibrations. Furthermore, they can withstand extreme temperature variations.
6. They are unlikely to build up sulfation
Sulfation is the property of lead-acid batteries, where there is a gradual accumulation of lead sulfate crystals in the cells. In most cases, it is the cause of failure in lead-acid batteries. Sulfation mostly occurs when the battery is not fully charged, and thus the crystals continuously build up on the plates. When this process goes out of hand, it prevents the efficient conversion of chemical to electrical energy. Therefore, for other types of lead-acid batteries, it is essential to charge them every six months to prevent sulfation. However, in AGM batteries, sulfation is significantly reduced. Therefore, they can be stored for extended periods without needing a recharge.
Also when I did my research I found that ALL of the AGM 6 volts (that I looked at) were SHORTER than the 6 volt LA. SO it allowed me to fit the TWO AGM 6v in under my step of my Axis with ZERO mods. It was a tight fit but they worked fine.
The OEM Harris 12 v tip my scale at 46 # each and the Full River AGM 6 V were 73# each!
They do cost more but IMO they are worth it.
Once your 12 volt LA are on there way Out and if your NOT going the Litium route IMO 6 v AGM are the ONLY way to go.