The Real DLC
If you're buying the complete pack of GT5 DLC, this is what you're probably really in it for. The detailed real-life Francorchamps course is a delight to race on (though I'm not a fan of driving in rainy conditions, it is available for this course and somebody must like doing that I guess). The Kart Space I and II are almost exactly the same track, with II simply having one less corner to worry about, but the course is colorful and cool to look at, like an unusually cool roller rink, basically. Plus the new 2.01 patch has just added the ability to use non Go-Karts on the Kart Space in online modes and free practice mode, so have fun trying to turn your Red Bull Prototype around in this tiny space I guess?
Both courses are a significant addition to the game, and the only truly worthwhile addition to this round of DLC, unless you like pretty car colors.