Regular instant ocean, imo is far insuperior. Maybe it was the fact that I got a bad batch, but it was lacking calcium greatly. Calcium is a very important thing for a reef tank and IO wasn't cutting it. I switched to Coralife, which also in my opinion isn't as good as others. I have heard good things about reef crystals.
This is from my experience, perhaps I just did get a bad batch of salt, but that is enough to guarantee that I will never buy it again.