If an applicant is experienced, has a solid work history, and is staying within her field, the most effective format for her resume would likely be "chronological".
The chronological resume is the most used out there, it’s the employer’s favorite as it is very easy to read and it’s hard to hide anything in it.
The functional format should be used when you want to draw attention away from your work experience due to job hopping, a very long career, a very short career, long gaps, re-entering the job market and so forth.