Hello Peter,
I run a Renault Grande Espace MPV, which I find to be a super tow vehicle, and may of the reasons why I like it will apply equally to the Alhambra/Galaxy/Sharan vehicles. The VW engine they use is well proven.
Load capacity, they will all swallow large volumes of people and luggage.
Flexible seating arrangements to suit many situations
Individually adjustable seats even for rear passengers
Raised seating which affords good views especially for passengers.
Generally heavier bodies that also moves towing ratios in a good direction.
Relatively short rear overhang, improves the vehicles control of the trailer.
Generally better fuel economy compared to 4x4s you might consider, along with better road manners and road tax.
I am generally happy with my Espace, but it has not been problem free, and I would definitely consider alternative makes when replacement is due. Others to consider, Fiat/Citroen/Peugeot, Kia and Chrysler.