There is a big difference between active material and weight, the AGM (absorbed glass mat) also called VRLA (valve regulated lead acid) battery is still lead acid like the flooded type, but it preforms far better, the problem is of course they can dry out, and no way to top up, so today batteries are put in the boot not under the bonnet with a hot engine.
It has also changed the way batteries are charged, early cars had a free wheel on the dynamo and an adjustable brush to regulate charge rate, on turning on the ignition the dynamo would motor, and then once engine started the engine would drive it faster and charge the battery, and the driver monitored the charge rate with an ammeter.
Since that time the batteries have not changed that much, but the charging systems have, the cut out and regulator took the control from the driver, but a typical two bobbin regulator was set to an open voltage of 16 volt, not that it ever got that high when connected to a battery, but volts were set high to compensate for when engine was just ticking over, there were some specials, bus dynamos had bucking coils to destroy the field as they were designed to charge at low engine revs.
Then the alternator, mainly three phase, some French ones were single phase, but the diode (also used with some dynamo regulators in later years instead of cut out) stopped any back feed, most were switch mode controlled, i.e. on/off not up/down and relied on the battery to even out the charge, most electronic control although some Japanese cars had mechanical regulators, and most were voltage only controlled although the AC203 used on buses had a current control, and they would start charging as the same revs as old dynamo, but could rev higher, so fitting a smaller pulley resulted in charge at tick over.
Only in last few years has there been a change, the stop/start technology and switching the alternator on only on over run, means the flooded lead acid battery can no longer do what is required, although back in the 50's we saw ideas to stop spillage and by the 70's there were maintenance free batteries, the AGM battery was used in mobility scooters, intruder alarms, and stair lifts, but not in cars, weight was not really a problem with cars, so only in last 10 years have we seen cars fitted with AGM batteries, used like the old flooded battery they should last longer, but used with stop start not so sure.
Even swapping a battery, it was simply a case of connecting a battery across terminals so as not to lose radio code, and fit new battery, but today need to connect a PC to the car and tell the cars computer that a new battery has been fitted, as the computer decides when the battery needs charging, and the alternator output is computer controlled.
So short trips and engine will not stop at junctions, only when the computer decides it has enough charge will that happen, and in the main battery held at 80% charge and every so often fully charged so it will not sulphate. So today you need to tell the computer what size battery has been fitted, as well as telling it one has been changed so the info supplied with the battery is important. If a battery is really 60 Ah and you tell computer it is 100 Ah it may get wrong amount of charge.
So you would need to in most cases get the battery changed by some one who has the ability to plug a laptop into the car, even the RAC man today has a laptop, driving around with a few tools in motorcycle panniers has gone. So has changing a battery DIY style, or in many cases the local motorist shop.
So when comparing makes, it has to be like for like including setting up car on the PC, and I have not seem any Lion batteries in my local Jaguar dealership so I suspect they don't have the info to set up car using a cheap battery. OK in my old Honda Jazz the batteries can be compared, but even if I wanted I could not really fit a Lion battery in wife's Jaguar XE.
Things have moved on.
