It mostly comes down to build quality. The kit lenses use less quality parts than most other lenses and therefore has less clarity, depth of field, contrast, they seem flat, bad bokeh, and even not as good performance with autofocus and holding up to the weather.
The nifty-fifty is superior in all those aspects. The fact that it is also a fixed lens, not being able to focus, is something I'd say is positive in the beginning. It teaches you to move into position for a good shot instead of just perhaps zooming. It makes you think and move your feet. So overall it would teach you positioning better.
A lot of my stuff is mostly product photography or for fake marketing purposes (my education). So I find them pretty boring in terms of photography. But I'll share some.
Some of these are shot with a 17-70 Sigma, and some with the nifty-fifty. Can't remember which is which really. The camera is a Canon 60D.
http://imgur.com/a/LCK7Dhttp://lindmarker.se/wp-content/uploads ... G_1492.jpg