Market pressure in the US has been pushing down the lowest salt levels that units will work at. Working at lower salt levels requires slightly more expensive components, but customers are demanding that they work with the lower levels. Manufacturers have been following that trend (some more quickly than others).
I wouldn't make the decision on the basis of the recommended salt level, unless you already have a strong opinion on that subject. It doesn't make any significant difference to the chemistry and the taste is very similar and not objectionable to most people either way.
Personally, I prefer Hayward to Zodiac, but not for any reason having to do with the salt level.