I use Reef Crystals because of cost and consistency. Instant Ocean is a world wide leader in marine salt. If you go to the large aquariums around the world and ask, 9 out of 10 will say they use instant ocean (unless they pump in direct from the ocean). They buy these monstrous 1 ton sacks that are HUGE! Because of their quantity, they sell their product for much cheaper than any competitor could.
I like Brightwell, because they are a great company, and make quality products. However, its costly and not quite as good as reef crystals in my opinion.
Aquavitro is great salt, and if you don't like to dose, this is your salt. Do a solid 10% water change weekly on a stocked reef tanks and you shouldn't need to dose anything.
I'd suggest the aquavitro with automated (or simplified) 10% weekly water changes to anyone who is interested in SPS dominated tanks.
I have tried many other salts over the years, but always go back to the Reef Crystals... I just wish they would bring back the screw top lids... I got rid of many of my old ones and now they have the pop top... BLAH!