Water type

go with convenience and less cost. unless you have exceptionally hard water, it won't mkae a difference. fwiw, i just switched from hard tap to softened water (convenience)... avoided it for 5 years and tested this run... absolutely no problems and no discernable difference from past results. don't use softened water if you can avoid, but in 3-4 months even 5, probably won't make a difference and less risky for methods that employ a consistent runoff when irrigating.