There are just a couple of applications, outside of the servers’ realm where the ultimate in performance is expected. Of those, the processing of video and high-level gaming are by far the most common. Both require all the power you can lay your hands on, and even that may not be enough to satisfy some users. At this level, you need to give up on portability for your heaviest lifting and nothing will do but a desktop. Power may be slightly limited in some ways with best of breed desktops, but expense, not so much. You can spend a huge amount of money on the fastest hardware in the land. For example, it is fairly easy to spend over $5,000 on a Dell desktop workstation, which does not even get you any peripherals. It’s hard to go that high with an HP, but certainly $3,500 is no problem. Gamers can easily spend $6,000 or more on the ultimate system.
The rest of us would probably be happy with a quad-core processor system including several terabytes of hard disk, 16 GB of memory, and a very fast video card, all in a nice case with expansion possibilities and Windows 7 Ultimate to orchestrate the whole works. A system like that can be found for around $1,000 and sometimes less, exclusive of peripherals such as display, keyboard, and mouse. Yes, it’s a little cheaper to get big power in a desktop than in a laptop, so if you never plan to take it out of the house, perhaps a desktop is for you.