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.
It used to be true that firms preferred to hire employed people because only the deadwood were let go from a company. However, in the past 10 years, corporate mergers and acquisitions, hostile takeovers, and right-sizings have put many highly qualif ied professionals on the street through no fault of their own. Prospective employers are aware of this trend. If you maintain your self-confidence and tell a potential employer what you can do for him, he will consider another firm's loss his gain.
A resume is an important tool, but it can't get you a job. Only people can do that. If you want your job search to be successful, concentrate on people and prepare your resume to suit their needs.