Title pretty much says it. What's the difference beteewn Pokemon Mystery Dungeon Red and Blue?
Is it exactly the same as each other, just with minor changes and the fact that one's for GBA and the other DS?
The available Pokemon are different in both games, just like the main series games. For example, Plusle is only available in Red, Minun is only available in Blue. You can use the mission codes to get the version exclusive Pokemon in the other game though.
Other than that, I don't think there are any other differences.