There's no real advantage from simply changing from a 190mm shell to a 200m one. But the 200mm shell does allow you to use offset wheels to increase the track width of the car. This allows the car to corner faster as well as a few other handling changes such as a slower reacting car. The BRCA requirement is for the max width of a 1/10th electric touring to be 190mm so I guess it depends how closely you want to follow their rules
HTH