You have to have kept both to understand both the pros and cons.
Saltwater is less maintaince than fresh, despite common belief. It can be a little difficult to get started, but once you've got it going you can sit back and relax.
The biggest pro in saltwater is what you can do. There is an endless list of fish to keep in saltwater, while most fresh "predator" tanks are pretty much the same thing, i.e. rays, arowana, tigs, catfish, cichlids, etc. In saltwater, there are enough different tanks to try to keep you going until you die!
The only major con is price- saltwater fish, and equipment in general are more expensive, but the reward is worth it. Some other cons include salt deposits, need for a skimmer, lighting requirements for some corals/etc, and needing to mix salt when doing a water change.
That's not to say fresh is bad, i love fresh myself, but seriously people, stop dissing saltwater!
And NO, you don't need corals, or even live rock in a saltwater tank!!! Although, they do look nice...