An AGM battery is a VRLA (Valve Regulated Lead Acid) battery.
I suggest you read this document someplace along the line to help understand what is expected of an owner and their AGM battery(ies):
http://www.cdtechno.com/pdf/ref/41_2128_0212.pdfFor what it's worth, we have had a couple of C&D Technologies (rebranded for Interstate) deep cycle 12 volt AGM batteries in our RV for 8 years come this November. They have been dirt simple to take care of and high on performance the whole time.
For the electric trolling motor in our fishing boat we used a special Group 31 90 amp hour Optima Yellow Top battery that is now at least 12 years old and gets charged once or twice a year on an inexpensive Sears plain vanilla single voltage charger. This battery now usually resides in the trunk of our family sedan as an emergency engine starting battery. Sometimes I take this 90AH Optima on camping trips to run my CPAP machine all night or run a 150 watt electric heater all night.
I don't know if Lifeline is necessarily "the best" AGM battery. FWIW, I wouldn't be afraid to try a Rolls-Surrette AGM battery over a Lifeline:
http://www.dcbattery.com/rollssurretteagm.html
