The StringBuilder class provides good performance for string operations with default attributes. And you can accomplish your string operations with in best memory performance adjusting StringBuilder Capcity property.
StringBuilder() sb= new StringBuilder();
And when you add some characters more then 16, it’s capacity raises 16, automatically. (32, 48 etc.)
If you are using some text with low amount of characters, you can instantiate a StringBuilder object with a capacity parameter.
StringBuilder() sb= new StringBuilder(6);
So the capacity of the object will become 6, 12, 18 etc. And the memory usage of the object becomes optimum for the case.