I just read an interesting article on functional resumes and I want to share a comment with you. They don't work. Reporters (like employers) what to know the what, why, where, when, and who. This is exactly the same as recruiters.
All the articles I've read contend that the candidate has "something to hide" by putting together a functional resume. If your work is recent, great, discuss it. If your experience (in your chosen field) is 10 years old, that could mean your methods of accomplishing tasks could be that old as well!!
Please consult with a career counselor (like me for example) to determine the best formatting for your resume.