Is easier to keep a salt water or fresh water tank?

Personally, I think fresh water is easier because a salt water tank means that you need to purchase aquarium salt, and you need to add it to every water change. I have never raised a saltwater aquarium, but I believe you also have to measure the amount of salt the fish need. So if you're a first-timer, go for the fresh water tank. But the good thing about saltwater tanks is that it is more diverse and colorful.