I have no regrets about this trend; cases of twelve are a bit of a struggle (especially down steep cellar steps..) and as most wine merchants tend to have only a handful of bottles of any given wine on display at one time, it saves them the hassle of having half empty cases in the stock room.
Perhaps in another twenty years, the 9 litre case will be consigned to history; in any event, I will then be in a much better position to opine as to which is my favourite Vesuvio!

Tom