It depends on what is actually in the computer of course; but in my experience laptop tends to be best for things that require mobility while desktop is better for when you need the raw power and don't need to move it around. Desktop hardware is generally more powerful, easily upgradeable, and easier to keep cool, but of course the big heavy tower isn't going anywhere. The laptop is usually harder to upgrade, is probably going to cost more to get equivalent power to the desktop, and many have heat issues, but it is of course smaller and easier to move.
If you could get both, then get a good desktop and a cheap but durable laptop for tasks needing mobility (you don't need much to stream and word process). If you could only get 1, and...