AGM I had a reproduction FLOODED battery in my '68 RR and then had a voltage regulator fail and over charge the battery. Of course, the battery sprayed the acid all over the engine compartment and ruined the paint. With an AGM there's less acid that would have escaped the battery as it is in the Absorbent Glass Mat. Also they are less vented and can be slightly tipped for some situations. Motorcycles such as dirt bikes and adventure bikes because of there bouncing and high vibrations use only AGM batteries. There's also Lithium-Ion batteries but expensive and maybe not worth it for your application but you could if you wanted mount them on their side, Just throwing that one out there.