The resume writing service does not require knowing anything about you. All they ask you to do is fill out a standard online questionnaire and maybe submit your current resume. A competent service needs you to fill out a questionnaire; however it does not end with this. They contact you and ask for numerous other details about your career and achievements that they need to create an effective resume.
Mass production may be suitable for nuts and bolts; however it sure is not the right method to create your resume. This is what the resume mills or factories do - produce resumes that all look the same. When a prospective employer receives hundreds of applications and your resume is similar to the majority of them the impression created is not good enough to warrant an interview. Most likely it will not even be viewed.
Functional format is best for those who are switching their career or have large employment gaps on their resume. In this format, you dont have to list the joining or resigning dates of the previous employments. Functional format will hide your employment gaps or your job switching.
The template of the resume which is actually the outline or the structure of the resume decides the positioning of every element of the resume. If this positioning is clear and clean with an equal weightage given to every element it appears that there is a flow in the format and so the resume appears attractive. Such a resume neither looks like a piece of art which shows that you were keen about the outline of the resume rather than the content nor does it appear as an essay.
There used to be a day when you could create one generic resume and then blast it to a wide range of jobs you were interested in applying to. Even if you are using a resume service this practice of blasting is generally frowned upon. HR professionals are inundated with resumes and they want to see that applicants have read the ad and are responding directly to it. One-for-all type of resumes are easily spotted and are generally discounted by HR. So work with a resume service to see how you can best tailor yours for each job you are applying to.