For most of Nintendo's systems, there have been no load times, except for the GameCube and Wii. With the DS, a level in the game loads up quickly, just like with Game Boy games. This is because cartridges can be read a lot quicker than CDs or DVDs.
The Nintendo DS is one of the rivals of Sony's PlayStation Portable. However, both Nintendo and Sony state that their products were aimed at different people, so there is "technically" no competition. The DS has currently sold more units than the PSP has.
Nintendo DS Facts for Kids. Kiddle Encyclopedia.