Reducing the amount of code does, however, make a big difference in modification of the code. The more code there is, the harder it is to modify correctly. There's more code to understand. You change this bit of code here, but the system doesn't do what you expect because you didn't change that bit over there that does much the same thing in a slightly different context. By eliminating the duplicates, you ensure that the code says everything once and only once, which is the essence of good design.