Expect a game very much like Dirt 1, but without the impressive graphics and damage model. New challenges and new look
First off, on the wii, you have single player and offline multiplayer (split-screen). The single player mode is divided into the world tour, where you have 4 event packs of rising difficulty level. The events let you do very diverse racing that spans from buggy racing in the desert to driving a toyota on asphalt. The first races are very easy and can be won even though u spin out alot. Furthermore, you have 20 challenges to try and beat, and there are time trial and championship modes as well.
There are 9 countries to choose from, and they have 1-2 tracks each. This is a bit disappointing. There are lots of cars to unlock though.
The graphics on the wii are rather disappointing, though the tracks are made very diverse. there are no environmental fog or lightning effects, which there are on the ps3 and x360 versions. The cars have shadows though, and when you drive under a tree, the shadow can be seen on the car, but it's not as impressive as the real-time lightning on the x360 version for example. Also notice that there are no damage model.
That plus no online multiplayer makes this the least preferable version. But if you only have a wii you might be satisfied anyway, considering the game runs at 60 fps, and have the same frantic gameplay as the other versions.
The price is still high, therefore I say rent it first. Mario Kart is still the best racer on the wii with it's 32 tracks and battle mode..