Generally speaking, and for my own needs/preferences, I would say a laptop. However, and it's a huge one: Something important about the distinction between laptop v. desktop was recently brought to my attention by the manufacturer of both my desktop and my laptop.

Read the fine print on any warranty and ask the unanswered questions.

If I hadn't had it in writing, the manufacturer could have fallen back on this caveat in the general warranty policy:

When a computer has a major hardware failure, some manufacturers will not provide the same in-home or in-office service as they will for a desktop computer or standby service/replacement (free to the consumer) for the hardware unless the costumer is willing to jump through hoops and kiss some serious y'know what.

Both the bold print and the fine print on the warranty on my laptop said nothing other than the manufacturer assured a 1-year warranty on hardware and the store (where purchased as a gift for me), a 2-year warranty on hardware.

No way, no how was I going to say, "Oh, I'll absorb the repair costs." I reiterated the text that accompanied the purchase of the computer and the packaging.

Anyway... read everything over carefully and ask about myriad scenarios re: system failure(s).