I think the main difference is to do with the way the vehicle's alternator and charging system charge the two different types of batteries, newer vehicles (built in the last 10-15 years or so, at least in the case of Ford) employ a 'smart charge' system which instead of charging a battery at a constant rate (IIRC) charge at a higher voltage from cold (as a cold battery is able to be charged at a faster rate), gradually reducing the voltage as the engine/ battery warms up, basically optimising the charge rate according to the battery's needs. Perhaps Mirez can explain this better than I can?
As the engine and ancillaries presumably including alternator and electrics in the V6 Galaxy you own are all of VW origin I would be more inclined to take heed of VW's recommendation on the subject, assuming you can find it, the upshot is that a standard lead acid battery isn't optimised to a system with smart charge designed to use a silver calcium battery and the battery recharge performance may not be as good as it should. How much difference this makes to real world everyday driving somebody else will need to quantify.
This link mentions smart charge on the paged numbered 196 (section 4), and a bit of blurb about silver calcium batteries on page 200, on the right hand side.
