Ultra Wide angle and fish eye

I went to Nikon Centre last week and tried out some of the lens there. One thing that always makes me a little confused is the ultra wide angle and fish eye lens. What is/are the difference(s) in the final result, ie, the photo itself. So, here they are:

This photo was taken using the 14mm lens at 1/60sec f/3.2 prime lens.

This one was taken using 16mm lens at 1/60sec f/2.8.

So, as the name suggest, a fish eye lens is made to produce a photo with "fish eye" view! The effect can be quite nice. But the question is, is such a lens still needed since photoshop can easily produce this kind of effect  on the computer. The above 14mm is definitely very pricey!