If I remember, Culligan is the one I used when I lived in FL.
@JoyfulNoise can give you a good breakdown of what to look for.
First you start with a water analysis of the water coming into your home. Ideally you’d like to know calcium hardness (CH), general hardness (GH) and if there is any iron present. Free chlorine (FC) and chloramine (CC) is good to know to. TDS doesn’t matter much as most water suppliers are required to hold that below 500ppm by the EPA but total suspended solids (essentially “dirt” ) would be nice to know. All this can be done be with home testing and/or mail-in testing (especially for iron and TSS).
Once you know what your raw water source looks like then you need to ask the following questions -
(1) What is my monthly water usage in gallons per day (both peak usage and average)?
(2) Do I have a service loop in my garage or mechanical closet that I can hook up to or do I need to install equipment at the main? What plumbing size do I have (1” pipe is typical)?
(3) Do I need to prefilter my water at all to lower TSS? (Not typically for municipal water, but sometimes it’s needed)
(4) Do I want to eliminate chlorine/chloramine from the water?
Once you have that information, you can properly size a water softener, set it’s processing and reserve volume, and add on any extra features like GAC or particulate filters. A modern water softener should use an exchange resin that is at least 10% cross-linked polymers or better. Cross-linking reduces the exchange resin capacity (how much calcium it can hold) but improves the resins lifetime by reducing the effects of chlorine oxidation.
If you have more than 1-2ppm of iron in your water, then you have a bigger issue on your hands. Iron destroys the exchange resin in two ways - it catalyses oxidation and it irreversibly binds to the resin reducing its calcium holding capacity. So, when high iron is present, you need to prefilter it. Unfortunately, that greatly adds to the expense of a softener setup because greensand iron filters are expensive and require a bit more care & maintenance than a hardness filter.
If you don’t need to worry about iron than the best setup for a hardness softener is a dual tank system where the brine (salt) tank is separate from resin filter. Clack control valves are considered the “best of breed” in process control valves. Fleck/Pentair valves are cheaper but not as reliable.