No real opinion on "Best" but I used to use Instant Ocean, then switched to Reef Crystals...probably about the time it had a quality problem.
I'm not sure at all if it's related, but all my nice RBTA's bleached to hot pink for A YEAR. Recently, I switched back to IO (mostly because I'm running out of RC) and ... some of the RBTA's are regaining their orange colour. Again, I have no idea if there is ANY correlation at all.
So now I'm using IO, and mixing in whatever RC I have left. I'm not sure if my batch of RC was affected by the quality issue...but as far as I know, the "quality issue" was just having RC buckets filled with IO...so in my case that basically means ...nothing! But I'm not sure if that was the RC issue.
I'll use one or the other of those, they work for me and I'm scared to try some other salt...I can see no advantage to switching to another salt.
V