There aren't any easy answers in software development because it's an art, not a science. In some circumstances clean code is better, in some circumstances efficient code is better and if deadlines and money are involved sometimes a complete hack job that's both ugly and inefficient is best. Whenever writing software you have to look at all your available resources, hardware, developers, money, time and figure out the best way to utilize those resources. If a hack job will pay for a rewrite and you don't have time to do it right then do that.