I got a new laptop recently that I do my writing and some coding on. For graphic design (and games!) I still use my old desktop computer since it is a P4 2.4ghz, definitely still useful. I forgot how nice it is to have a laptop until I got my new one recently
I find that my productivity is higher, working on a laptop. Hence I've been using laptop, even at home, for the past 3 years.
I use a laptop so I can work where ever I am. I don't think I'll ever buy a desktop again, I would prefer to have my laptop on my computer desk just incase I want to move it.
I use the desktop when I am at home and laptop when on the move. I find the desktop to be more convenient to operate
Using desktop in my office (office hours 10 to 6) and using laptop at my home (home hours morning 6 to 9 and evening 7 to 11-12) DON.
I would have to go with PC. Laptops are just too small, plus I have multiple moniters with my PC and couldn't do without.