I once did a comparison for someone at work.
In short, if you need portability, get a laptop. If you don't, why get one?
I find them uncomfortable to work at for long periods, as I'm sure any workplace assessment would agree with.
They are harder to upgrade/maintain, more expensive, and less 'bang per buck' than desktops.
The only real justification in my mind is if portability is likely to be a requirement, otherwise I'd go desktop.
Just my 2p worth.