I'm sure you might have opened a can of worms here, for you can not really tell whick one is better. It's like asking if a dog or a cat make a better pet. Dog lovers will go for the former, cats lover for the lattest. Some will love both and other will hate both too.
However, there are some guidelines you can call to make YOUR OWN desicion:
1- Color display: if you look at freshwater and salwater aquaria pictures, you'll notice how normally a saltwater reff tank shows more color than a freshwater similar tank. Saltwater fish commonly sold for the hobby are generally more colorful than their freshwater counterparts. Also, odd creatures are more likely to be found in saltwater tanks (starfishes, for example).
2- Fish capacity: in the other hand, if you like to see lots of fish in a tank, freshwater allows you to put more fish in a certain surface/volume of water than marine tanks.
3- Cost: a marine tank is more expensive to set up then a freshwater counterpart. Fish are more expensive, and some material used in FW aquaria will produce problems in saltwater tanks bacause of the corrosive salt. Also, the most eyecatching reff tank setups require expensive ligth systems that consume lots of electricity.
4- Difficulty: setting up and maintaining a marine tank normally involves more water chemistry and work than a freshy tank. Also, water parameters are more forgiving in freshwater tanks than in a salty aquarium.
5- Plants: saltwater tanks have virtually no selection of plants that can be raised in the tank. Freshwater tanks can become true underwatwer gardens if properly maintained. Also, tle paladium is a freshwater setup where plants grow outside the tank and populate the rear wall. Wonderful.
These are some thought that just jumped into my mind, and are general approachs to the truth.
My freshwater set up can become more expensive then my friend's marine depending on what I decide to put in there. Also, I can work my fresh water so hard to make it perfect for my tank that the dificulty will match that of recreating sea water.
So, there is no definite answer to your question. Look at some pictures in the internet, ans you'll see a lot of differences among different types of tanks.
). the work involved in a freshwater tank jsut seems a little easier, there isn't as much equipment to buy (has anyone ever needed a protien skimmer for a FW tank?), and if you do things right a FW tank can be every bit a beautiful to look at as a SW tank. that's my opinion anyway 
