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.
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.
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.