Pick the service like you pick any other service. Word of mouth from people you trust, reviews, research into the service, common sense, money-back guarantee etc. How do pick how to use any service? How do you pick an important SAAS or library or API to use?
If you are so convinced you wouldn't be able to tell if a service is doing a good job, how do you know that this recruiter you went to "butchered" your resume and didn't improve it?
Sorry if I'm coming across as overly combative, I just feel that IT professionals in particular are really bad at acknowledging their inexperience in other domains. I think this is especially true when it comes to writing. Perhaps it has something to do with documentation traditionally being an afterthought in the FLOSS world.