I've used Tropic Marin, Instant Ocean and Coralife.
We are currently trying out the Coralife salt and so far we like this the most. Corals have never looked better.
I don't think they are different content wise, but for whatever reason, our tank looks a lot better with Coralife salt. Also, the salinity stays more consistent now as well.
I had no luck with SPS with Instant Ocean.