A Google interviewer will ask this question to determine if you are a good fit for their organization. There are a lot of different methodologies software developers can choose from. Regardless of which one you prefer, you'll need to adapt to the software development methodology used by the organization with whom you are interviewing. You can learn about the methodology Google's software development team uses should through your pre-interview research. The method you state a preference for should align with the one the company currently uses.
