I am pleased to be able to renounce this verdict, at least in part.
The flavour of all our tomatoes has improved!!! We are unsure as to the exact reason for this, but suspect it may have something to do with more water (we had some decent rain), and the tomatoes getting into their season properly (early fruit never being the best?). Whatever the cause, I am happy. I would not go so far to say that I am rapt with either variety, but they are definitely palatable. I think I prefer the typical cherry tomatoes myself, which neither of these is. Next year I will probably add a popular cherry variety or two, but will also grow a few bushes of each of these ones for variation, particularly as they seem to both do well as soups, sauces and dried fruit.
Principe Borghese ripening
Sometimes it pays to reserve judgment until all the data is in, don't you think?