Notebook computers can be incredibly convenient for anyone who needs to travel or work in multiple locations. While external hard drives and flash drives can be used to carry around a hug amount of data, being able to work on the same machine, one that's been configured by you for your specific needs and style, is a major attraction. And with a notebook computer you can do a little work, or watch a video, surf the net, etc almost anywhere you go. You can not do that with an external hard drive.
Prices have dropped and performance has improved, but you are still going to have to make some compromises. Substantly more powerful and flexible desktop systems are also now available for prices that are quite a bit lower than any reasonably well configured notebook. You have to pay a premium for your notebook's portability. Notebooks are also less comfortable to use than a desktop system, though this can be corrected with an external keyboard and a mouse – but, you will not be carrying a full size keyboard around when you travel. Ergonomically, notebook computers are simply impossible without external devices. So you also incur a comfort penalty. And usually the notebooks keyboards are more compact and may not have all the keys you'd like. Finally, they are also typically configured differently than full size keyboards. This can affect your productivity to some extent.
A desktop system is typically pretty easy to upgrade – even to add additional devices to. It can also usually handle more memory than a notebook computer and run a more powerful processor. Notebook computers can be hard to upgrade and your options can be quite limited. They generally have just two memory slots and are limited to maximum of 1 to 2GB of RAM. Replacing the memory is probably the only upgrade that will not require a specialized service center.
And unlike desktop systems which are reliably easy to repair, notebook computers are not only difficult to repair and require specialized, highly trained technicians, they also require specialized parts. If they are even available. I've built 5 or 6 computer systems for myself from scratch as well as upgrading them, adding more devices, etc. It is not all that difficult. But mess with my laptop? Not a chance. I've upgraded the memory and that's it.
So, when a desktop system goes belly up, I'll replace the mother board (or whatever component failed) – or start from scratch and build a better system and recycle the devices that are still useable. However, if my notebook computer develops a problem, I've got serious and probably expensive trouble. Almost anything that goes wrong is going to involve specialized components of one kind or another. Remember that it takes some manufacturing ingenuity combined with miniaturization to cram a reasonably capable computer into a notebook case. So if you get yourself a notebook computer, make sure there's a service center nearby or be very clear on what you'll need …