Has anyone tested the hardness of your water?
Great place to start.
Some other things to think about, or make sure your vender thinks about:
Your demand - is it around the clock 24/7? If so, you'll want a twin tank alternating softener.
If not, a single tank softener should do just fine.
What is the max reasonable flow (gallons per minute) you're looking to treat? Higher flow = larger softener.
What is the daily volume (gallons) of water you'll want to treat? A softener that is too small will have to regenerate too often.
What is the minimum flow (gpm) you'll treat? Will this be a common situation? Will it persist for more than a few minutes? Slow flow through an over-sized softener can caused channeling and degraded performance.
Does the softened water feed an RO system? Is that the only target for softened water or do you also feed softened water directly to the bays?
What is the diameter of the feedwater pipe that will be supplying the softener?
Consider the brand of valve in the proposals. Fleck is a little cheaper up front (typically, but not always). Clack is much more user friendly when it comes time for maintenance. Or are they proposing an Autotrol valve? Or some off brand? We are a fan of Clack valves. Just put a huge Clack twin alternating softener in a distillery - each tank contains 30 cuft of softening resin.
Russ