There are currently three broad categories, each of which can be subdivided, of devices that users can now choose from:
Mobile: This category includes both handhelds (mobile phones and devices like the iPod Touch) and tablets. While these each solve a specific use case within the category, they all have mobility and a touch-first interface as their two primary features. They also provide their users with a task-based focus through the use of apps instead of applications.
Strength: Portability of the device and the focus of the apps.
Needed Leverage: An always (or almost always) available internet connection for extensive file storage.
Weakness: Not as powerful, in terms of computing power and application flexibility.
Laptops: This category includes all devices that are portable but require a keyboard. Yes, they may have touchscreen capability, but the primary input is designed to be through a keyboard. They share with their desktop-bound counterparts an approach to tasks that uses application, rather than apps. This represents not only a difference in focus but also in the number of tasks that a user can pretend they are dong at the same time. While the latest iPads can run two apps at once, laptops and desktops can have multiple windows open at the same time.
Strength: Balances the power of the Desktop with the Portability of a Mobile Device
Needed Leverage: Consistent access to power to recharge its battery.
Weakness: Heavier than a Mobile Device.
Desktops: These devices are designed to stay in one place and provide significant computing power. Quite frankly, they provide far more computing power than most users need. More important for most users, these devices provide a significant amount of on-device storage for large libraries of files.
Strength: Raw computing power and the capacity for a lot of local file storage.
Needed Leverage: An Internet connection for off site remote access when you are away from your desk and a device to access things while out of the office.
Weakness: Immobile and, for some, too many windows.
Seen in this light, the laptop, which was once the way to get work done on the go, is now a compromise device -- a role usually given to mobile devices (It should be noted that this role is usually assigned by people who use laptops.).
It is also worth noting that there is no longer a primary/base-line device for people to use. All three categories are viable computing choices for users. The question, then, is what does the individual user need at the time (given the constraints of their purchasing power). This is something that strikes home every time I come to Asia. You do not see people using laptops as a primary computing device. You see them using a larger mobile phone. It is a trend, incidentally, that educators should keep in mind, as students everywhere appear to be shifting toward this model and it represents a shift as significant as the move from punch cards to keyboards and text-based to GUI-based operating systems.
The importance of use case here is a critical one in education, which has three primary user groups: students, faculty, and administration/staff. Of the three, the individuals most likely to be tied to a desktop are the administration and staff, who work at their desk (when they are not in a meeting). Professors are semi-mobile users, as they move from their offices to a classroom. Students, however, are clearly mobile users. They move from place to place throughout the day, as they go from class to class.
It is worth keeping this in mind when making decisions about the technology that students will be issued or be asked to purchase on their own. Mobility and portability, although they may not always recognize it, is an important factor in their interaction with technology.