This work introduces an approach to mine field-tested design solutions when defining the architecture of a new product line. The design comparison approach (DCA) compares design solution alternatives implemented in existing systems and evaluates their advantages and drawbacks. This explicit comparison and analysis enables the development of high quality product line architectures by incorporating field-tested, proven concepts and strategies. The experiences gained so far in case studies support the claim that the resulting architecture profits from the application of the DCA approach.