I find this is a personal preference. Some people really like laptops while others prefer desktops. That said, I think the state of art for laptops has reached the point where they can be, in most cases, as powerful as desktops. The only thing you won't find in such a laptop is an extended battery life.
Well, I'd give Apple's Macbook Pro line a try. They've got awesome battery life (10h) You really don't know what you're missing out on until you've worked on one while on the road. Of course, the price tag ain't cheap...
It depends what you use the computer for - gaming, 3d rendering, etc I would go for a desktop because they can be way more powerful, but if you do graphical, coding, programing work then opt for a laptop because it is easier to carry your work around, etc.
Depend on your needs actually.
if you are station and need max performance use laptop
if you are mobile and application usage is imp the go for laptop.
but if you require only word processing and mail and browsing try out tabs they are new in town and gaining popularity.
From my personal point of view, desktop have my vote. I have desktop and laptop. I use desktop to do design work ( large screen is much much better ) and i only turn on my laptop once or twice a week for casual uses.
I'd say the question is not asked correctly. IMHO you can't ask
what kind of car is better 2-door sport or truck? Plain water or vintage wine?
You wouldn't move old couch in sport car, nor celebrate your anniversary with just water bottle, right?! ;-) You know what I mean...
It completely depends on your needs and 'taste'.
I use a desktop-replacement laptop around the house. I can still move it to the living room for some casual browsing, to the kitchen to have that recipe handy or to the garage to have the repair manual open, but I still get a full keyboard and a 17" screen. It also uses less electricity than a desktop system. I don't do any gaming or heavy 3D stuff.
For work, I use a 15" laptop, but I have a real keyboard and mouse hooked up to it, in addition to a 22" monitor. It's still easy to pack up when I need to do work in the field or at the colo. A netbook might be more convenient for that stuff, though.
My media player is a little nettop, with Atom and ION inside, untainted by m$.