I've used red sea coral pro since I started the hobby and I was very satisfied(used it for around 6 months), but then, I didn't have enough experience with other reef salts to be in a position to have an objective comparison. Then a few months back, red sea coral pro became unavailable because the company reformulated their salt, so I was forced to try salts like Teco reef and Oceanpure. They were "okay" replacements but I always felt like there was something missing and I always had problems with them not fully dissolving and the tank clouding up right after a WC.
When the new Red sea coral pro salt came out (black bucket), I decided to try it out, and I've never been happier with a reef salt's performance.First of all, it dissolves instantly and leaves no residue, but the best part is, my corals seem to be more colorful, my zoas have bigger polyps, and even my crocea clam opens up more. Alll in all, I give it a 9/10 (I'd give it a perfect 10 but there wouldn't be any room for improvement).
I think the problem that some people had with it has something to do with the sudden shifting of salt mixes, there are very minute differences in the trace elements contained within each type of salt mix, and the abrupt change in these levels may cause some LS to react negatively. I've always found that the best way to change salt mixes would be to slowly introduce the new salt over a few weeks and a series of water changes(e.g.75% old salt mix+25% new salt mix for the 1st water change, 50%old +50% new for the next wc, 75%new +25% old for the 3rd, and so on...)
P.S. This is purely based on my experience and I've never done any type of experiment to really compare all the mentioned salt mixes. HTH