Many thanks to everyone for the replies and links. Very helpful and indeed
illuminating: I've decided to embrace the traditional technology.

I see that Monarch, makers of that no-salt unit, also have a conventional
machine in their catalogue: a two-chamber block-salt model which seems very
similar to the Kinetico softener I had at a previous house. The most
obvious difference is that the Monarch is about half the price. Searching
for reviews and opinions online I have so far failed to turn up a single
one, which might or might not be significant.