HT Games
Portability
The most obvious benefit of handheld games is their portability. The devices are small and light and are designed to fit in your pocket so that you can play them while out and about. You can play battery-powered handheld games almost anywhere--on the bus, in the bath or while in the waiting room at the dentist. This isn't possible with larger gaming consoles and computers, which need to be plugged in and set up in a fixed location with a TV and often an Internet connection.
Convenience
The portable nature of hand-held devices makes them more convenient to just pick up and play in a spare moment. You may feel you need to dedicate more time to sitting down with a console, plugging it into the TV and waiting for it to boot up. With hand-held games you can start them up in a flash, put them down for five minutes, or even have a quick game while watching TV or waiting for the kettle to boil.
Power
The greater portability of hand-held devices comes at a cost, however. Because of their small size, there is simply not room in hand-helds for the same amount of hardware and technology as larger consoles and computers boast, meaning that games do not have the same sophisticated graphics and range of game play. Many console games can have full HD and even 3D graphics, while hand-helds are restrained by the size of their processors and screens.
Display
The small physical size of handheld games means that they are played out on a much smaller screen than traditional consoles, which are simply hooked up to a TV, making them easy to play. Nintendo attempted to address this in 2009 with the DSi XL, which features a 4.2 inch LCD screen. The screen's resolution however is the same as that on the smaller DS models, so the picture is just stretched out--the graphics and levels of detail are unchanged. It is also 100g heavier than the original DSi, at 314 grams.
Multi-Player
Because hand-held systems are primarily one-player affairs, designed to be held in the hands of one person only, for a time it was difficult to develop multi-player games, which have been successful on the larger consoles. While wireless Internet connections now mean that hand-held gamers can play against each other, this means you need two separate systems to play. On a console, you only need two controllers. This can give hand-held gaming a slightly more anti-social edge than larger consoles, which are more suited to multi-player.
Cost
Because they are much smaller and contain less sophisticated hardware than large consoles, hand-held game devices are generally relatively cheap. Because of the inferior graphics, the games played on them are also less expensive, as they do not have the same lengthy development cycle as major PlayStation or Xbox games, some of which have the same production staff and budget as Hollywood movies.