After having a tank my whole life and coming up on freshwater, after switching to saltwater I must say the intricacies and diversity of owning a saltwater tank is much more rewarding than freshwater.
I've always gravitated towards the 'unique' fish on both sides. My freshwater tank had an African Ghost Knife, an Elephant Nose, a Sicilian Black Worm and the usual Black Marble Angles, a Clown Loach etc. Nicely landscaped with some petrified rock, bubblewall, live plants and the such. Do some water changes, wash a filter and that was it... the tank always stayed the same...simple and easy. However, with saltwater, I find the longer the tank thrives, the more things grow... Coraline Algae, Tiny Star Fish pods
, sand sifting snails. The fish are much more exciting in my opinion too. I have a Pinatus Batfish I've kept in captivity for over 2yrs. The colors and variety of the fish are amazing, especially colors under the right lighting. Soon, I hope to move into the coral phase of saltwater. Opening my eyes to a whole new world of beauty. As far as filtration and water changes go, some may say too much work, but if you love what you do, you never work a day in your life.
Either one will always be a matter of opinion. Freshwater is an excellent gateway into the hobby. But if you really want to get involved and enjoy a challenge, you will move into saltwater. If freshwater is a planet, saltwater is the universe. After all, it usually starts with a fish, in a bowl, on a table.
That's my opinion.