Only advantage laptop has against desktop is ability to easily carry it around. Desktop has more computing power and much cheaper parts. Desktop is much more durable and easier to upgrade. Also it's not so easy to "forget" desktop somewhere while laptops are lost very often.
(Pressed save changes too early)
Basically laptops and tablets are for casual use. Doing anything more serious is much easier with desktop. Even good keyboard+mouse is good enough reason for this. Then again nowadays there are much more casual users than before.
For things to look at desktop depends on what you are planning to do with it.
Edited by Drillingmachine, 17 April 2016 - 06:42 AM.