DS: The Grid is experiencing power outages, causing programs to resort to their most basic functions due to a lack of energy and start attacking everyone. You are a new system monitor assigned to investigate the situation.
PSP: You're a program who is trying to win the Game Grid championship.
Clearly, the DS version is the better game of the two. But at least the few opening scenes of the PSP version are satisfying--it opens at Flynn's Arcade in 1985, with Flynn in his secret hideout, developing new grid games tech--like new light cycles, for example, that can jump. You start the game as Tron--testing out the cycle. Then, you hire a recruit to enter the grid games and the story pretty much stops.
To those who have beaten the DS version......what's causing the power failures? Is it just that the Grid is too new at this point, and Flynn is overloading it with too much information at once? Are the hard drives storing the Grid outdated and too small? I spoke with a character in Tron City who said it had been "over a billion cycles" since it had been defragmented. Odd, because the game is rumored to take place in 1984--a billion cycles couldn't have happened yet, could they have?