There isn't a best. Every salt has pros and cons. You can use whatever your goal would be, like if you wanted more calcium in the mix you would get one that is higher in calcium.
At the end of the day, myself and several others mix things up. I simply order whatever is on sale at the time.
I agree that there is no best salt. If there was then everyone would be buying that brand. I use Oceanic because of the higher calcium readings. That is the Pro, the con is lower alk readings. As sniperhank said they have their pro`s and con`s.
You can view many of my fish and corals in my photo albums in my profile.