Auto Racing: Gears in the differential, torque multiplication, overdrive transmission

Question
I'm a little confused about the gears. One of The cars i'm looking at has 3.55 gears in the back. And it's labeled the "performance package". but also another car is equipped with a "track pack" with a set of 3.73 gears in the back. From what i understand one car is gonna launch faster than the other. What are the disadvantages of the one that launches faster than the other?

Answer
The higher numerical gear (3.73) is going to raise your engine rpm higher than the 3.55. This can be annoying if driving on the highway at a constant speed like 60mph. The higher ratio increases the torque multiplication as it is apploed to the rear wheels. It will give a better stoplight to stoplight performance. Increased wheel spin may result if performance tires ane not used. If you have an overdrive transmission you may be able to use the higher gear on the highway due to the reduction by the overdrive ratio.