Both set ups are very good.
As you point out that there are some pros and cons to either..
What was the water test?
The SXT can go to a higher gallon setting while the older style has either the standard or ext meter... so there is that part of the 9100.
The SXT can do a bit finner tune in the gallon settings, timer settings... and can be set for a day default where the older style can not.
I would take either one, for me to pick one it would depend on the house, water test and number of people there at the time.