You know you need a water softener, and you've been looking into the options, but you're still hung up on whether you're going to go with which type of salt you're going to use in your system. This is an important choice to make.
From the start, it looks easy, right? Sodium chloride (NaCl) is the salt you're familiar with, and it's also generally quite a bit cheaper. It's the practical choice if you're deciding based on on budget alone, but slow down and think about it. Just because it's the most obvious choice on first glance doesn't mean it's the best choice.
The first consideration you need to make is medically based. Do you or does anybody in your household have a sensitivity to either sodium or potassium? Some people have to be on a low-sodium diet, and using NaCl does introduce salt into the water supply. It's in small enough amounts that most people don't notice it, but it could have medical implications. You may want to talk to your doctor and see if they're concerned about it. If so, you may want to use Potassium Chloride (KCl), though you could also install a reverse osmosis filter for your drinking water. You could also have your softener installed so it only softens bathing/wash water and doesn't impact your kitchen; that's up to you.
The flip side of that is some people need to be careful about the amount of potassium they take in. There are certain medications, especially, that can raise potassium levels. If you or a family member have been warned against eating bananas, you should speak to your doctor about whether or not it's a good idea to use KCl as in your water softening system.
You also need to consider what happens with your waste water. Every so often, your water softener will need to recharge the resin beads that pull the minerals from your hard water, and this results in a heavily salted mixture being dumped into your waste water. Some municipalities have asked their residents to be careful of the amount of salt they dump into the waste water, and some have even gone to the extent of banning water softeners because the water has become too salty for the current systems to deal with. If the salinity of your water supply gets too high, it could have an impact on the environment as well as your town water supply. (If you need a water softener, odds are you're not alone.) If you're using well water, that may be a different story. You might ask your septic specialist about what they recommend for this.
Do your research and be informed so you can make the best decision for you and your family.
To learn more, contact a resource like Water Works Colorado Water Purification.