i only have freshwater right now, but i think both are awesome
freshwater has some huge species that are relatively easy to keep, whereas saltwater species of the same size would need a bigger tank and much more care
plants & driftwood make for a very nice tank layout, and freshwater is rather easy to maintain, quick to set up/cycle and also cheap
saltwater is pretty awesome in terms of variety of life even in small tanks...so many invertebrates

in a tank with 25l, you can have a few shrimps, snails and maybe 1 or 2 fish species, that's more or less it in freshwater if you don't count the plants
in saltwater, there's anemones, mantis shrimps, sea stars, crabs, fire worms, clownfish, 2-3 corals, not to mention tons of smaller inverts
and many of these come with live rock...the concept of live rock is just so awesome
forrest gump's mother would say: "live rock is like a box of chocolates, you never know what you get"

i definitely want a nano reef or, even better, a normal reef tank, one day
