At a given price, you are usually buying less computer with a notebook than with a desktop. That being said, there are a number of modern notebooks which are actually classed as "desktop replacement" computers. Please note, though, that due to cooling and power consumption restraints, you are unlikely to find a notebook to compete with the absolute top-of-the-line desktop. For normal computing, though, once you connect an external monitor, keyboard and mouse to a relatively decent notebook computer running off of AC power (to allow maximum performance), you would likely not be able to tell the difference. Notebook computers can run as fast as most desktop computers. There are limits to notebooks, those being space and heat dissipation, so the highest end notebooks are not on par with the highest end desktops.