Don't over think it.
Use the salt that is convenient to you and what you can afford.
On a smaller system, if you want to go fancy, go for it. But large system, I wouldn't go broke on salt. Stick to the one with consistency and you'll be fine.
I wouldn't lose sleep over a salt brand that is a little low on ALK, CA, or MG. The water change percentage you should be doing will not affect your overall system parameters in any meaningful way.
For example a 10% waterchange will affect your ALK this much using salt that is presumeably low at 6dKH and you keep your tank at 9dKH.
(9*0.9+6*0.1)=8.7dKH. This is well within your test kit tolerance and will likely be even out with your dosing or ca reactor.
I've been using IO for all the above reasons. Weekly 10% water change and a ca reactor is all I do.