.
My Mini has an AGM battery, while my GTI has an EFB. Both are still the factory
ones (Mini: almost 10 years!), both cars came with start/stop and recuperation
tech (I disabled start/stop). However there's a difference in where the batteries
are located and that points to a technical difference between these batteries.
EFBs are superior to AGM batteries in some applications. AGMs don't like heat,
which isn't an issue when located in the luggage compartment (BMW, Porsche)
or separated from the engine bay (Mini), though it could be an issue longterm
when sitting in the engine bay.
No idea if this could be compensated by improved insulation, at least it would
reduce peak temperatures. Of course EFBs are also cheaper compared to AGMs.
Just saying, most automotive engineers aren't stupid, there are valid reasons.
.