OK, read through the first page of the article posted on Advanced Aquarist. I am not at all concerned with the 9ppb listed from Tropic Marine Pro and the 3-4ppb difference between the tests on TMP and the other companies, wouldn't sway me one way or another.(we are talking parts per Billion here, not the parts per Million we typically test for) This is listed as the major concern the test had with the product.
In addition the PDF file you posted lists Tropic Marin Pro as having less copper then the average, so the two articles fight each other on that point.
I realize you, Chris, weren’t trying to say that TMP was any less than any other salt, but thought I should look at those articles again since it had been several years since I read them last. If those tests show no definitive strength or weakness to any of the salts that make them stand out as the best salt then I go back to my experience and the reputable opinions I’ve heard from others.
Again if you have cyano problems or are losing animals then the brand of salt may not matter as much to you, but I like and use TMP. If it weren’t available at all because they stopped making it I would use Brightwell. I’ve been out of work for many months and still use TMP. All above my opinions as the original poster asked for opinions.