I would think discus and SW would be about equal...although with different problems. Both require excellent water quality to do well. With SW, you have more water parameters to watch and maintain. With discus, water needs to be VERY clean and, in most cases, soft and acidic. Many people who raise discus advocate daily water changes...some of them even have a setup that continuously changes small amounts of water. Cichlids are a little more tolerant in most cases. They can handle a wider range of pH and don't require perfect water parameters.