I service computers and i prefer the laptop, just because its easier to get into it and find the problem.. not only that, but you can also hook up a desktop moniter to a laptop and use it as a desktop.. depending on your laptop or desktop.. im using a HP pavilion G6 from the G series.. and i honestly love it.
Ofcourse, desktops have advantages, like a larger memory or better graphics, but a laptop has its advantages too, like its portable. Desktops have a better protection against the weather (what i mean is, where its at and if theres alot of dirt and grime around it). Some laptops are customizable, different colors or a LED keyboard(which is what im workin on getting).
Desktops are usually faster than laptops, but they are more liable to get viruses or other things you dont want, now im not saying a laptop isnt just as vulnerable, but like i said:
So i prefer the laptop over the desktop.