There is no universally preferred format. Many job seekers spend days perfecting their resumes, agonizing over whether to use a chronological format or a functional one. This question may be akin to figuring how many angels will fit on the head of a pin. There is no one perfect resume to suit every employer's needs. But there is a perfect resume for a specific opportunity. If you are going to focus on perfection, do it on an individual, rather than a global basis.
Resume search is important for the job interview, too. Most of us are more comfortable moving into unfamiliar territory if we have a map of the terrain. When you have researched an individual company to tailor your resume, you know a great deal about its products-- services, mission, philosophy, revenues, and so forth. This information can be very valuable in preparing good questions and answers for initial and subsequent interviews. Employers like candidates who are savvy enough to do some homework before their first meeting. In customizing your resume, you are pursuing two objectives simultaneously: You are creating a powerful written sales tool, and you are developing a verbal testament about why a specific employer should hire you. If you think of your resume-writing process as the best preparation for a rigorous interview session, you will be more likely to give it the time it deserves.
My first six years in the business were hopeless. There are a lot of times when you sit and you say "Why am I doing this? I'll never make it. It's just not going to happen. I should go out and get a real job, and try to survive."
George Lucas