CAn't compare AGM to Flooded deep cycle under heavy loading. AGMS shine at holding their voltage under huge loads. Lifeline has the thickest plates in the AGM world and thick positive plates is the hallmark of a deep cycle battery. Odyssey and Northstar tout their Thin plate pure lead technology, and have extremely high CCA figures.
A 105AH group31 lifeline has 650CCA, a 100AH group31 Odyssey AGM has 1150CCA. In the voltage under heavy load contest the Odyssey will win. In the amount of deep cycles accumulated before battery failure, the Lifeline will win.
The T-1275 has 150AH capacity, a pair of t-105s 232AH capacity. Their plate thicknesses are comparable but the single t1275 weighs 82 Lbs, a pair of t-105's weigh 124.
Please keep in mind Peukert.
His law states the higher the load on the battery, the less available capacity the battery has to give. All batteries have some peukert component and some batteries are better than others in this regard.
Peukert basically says a 100 amp hour battery can power a 1 amp load for a hundred hours before voltage hits 10.5v, but it certainly cannot power a 100 amp load for an hour.
Far too many people discount Peukert's effect on their batteries when trying to figure out how much their microwave is using to bake that potato.
Peukert also works the other way too. A 100AH battery can power a 5 amp load for 20 hours before voltage drops to 10.5v. Loads under 5 amps will increase overall capacity available, but loads over 5 amps decrease it. Those who have very little loading of their batteries and do not approach the discharge rate at which their battery met its rating, will be able to go a lot longer before they can notice any capacity loss of their battery.
People tend to view Inverters as magical/ make everything just like a stick and brick, but there are huge factors that come into play when one is powering HUGE loads, like a microwave or a coffee brewer.
Jim in Denver has a lot of AGM capacity, and a heck of a lot of Solar, and can do things us mere mortals cannot.
But newbies to the 12v world seem to think they can get a small inverter, plug iut into their dashboard ciggy receptacle and power their hair dryer.
Jim might be able to have his wife blow dry her hair on Battery power, but few other people could manage this significant accomplishment.
There is also a tendency to get a huge inverter, just to have a big overhead, without realizing the battery capacity they have could never power the max rating of the inverter for more than a minute or 2.
While running the engine while inverting huge loads can offset a lot of it, it really depends on the vehicle, and the wiring to the house battery from the alternator, and the capability of the alternator. If the wiring is thick, the battery depleted and the loads is huge, then Idling the engine, well the alternator will quickly heat upto 220F and beyond if it does not have protections built in. With a huge load on it, the alternator WILL heat up faster than a cold engine.
The alternator does not make free energy. When Idling, with a capable alternator, the internal alternator fan is not moving enough air through it. Combine this with little underhood airflow at Idle, and one can easily fry their alternator.
Just some things to be aware of. Inverters are great tools for both quick battery depletion, and the frying of alternators.
Inverters can also be electrically noisy, and screw with the host vehicle's engine computer. I've read more than one report of the Use of an Inverter on a Dodge van 1994 to 2003 while driving have caused driveability issues. I've not experienced this, but then again I rarely use my inverters.
So anyway my point is they INverters and battery capacity should be designed as a system, and any offsetting of huge loads by running the engine, could contribute to the premature demise of the alternator, as idling under a huge electrical load is the best single way to overheat an Alternator, if that were the goal.
I've been Deep in Baja with a failed alternator caused by simply overloading and overheating it. It was quite stressful as I was also out of water and food, and my batteries were down in the low 11 volt range.
I could not have accomplished that without my inverter.
