There really is no "best," and all of the services will have happy and unhappy clients, based on their results, which are 99% dependent on the applicant. Plenty of folks get into Harvard with no help from a consultant, and all the services have clients who have unsuccessful cycles.
Believe it or not, I think the "best" is participation on SDN. People here volunteer to read and comment on personal statements, and there is a ton of activity regarding all aspects of an application that is generously offered free of charge by random nobodies like me, as well as by actual, live, current directors of admission, faculty on staff at med schools, members of admissions committees, attending physicians, med students, etc. They are much better placed to provide current, accurate information that random staff at consulting firms set up to exploit your anxiety and take your money.
If money is absolutely burning a hole in your pocket, and you are committed to leaving no stone unturned in your quest for success, I would recommend checking out the people who identify as consultants here on SDN, all of whom seem to know what they are talking about. Just pick one whose approach vibes with your own.
Beyond that, most of the big companies put up a ton of free content on YouTube as a loss leader to suck you in, so that's probably worth checking out as well. Finally, many of the prominent companies also publish books that you can buy on Amazon. I got what I needed from that, plus SDN, and stopped there, but you can start with highly rated books, sample a few, and then reach out to a firm and go from there. Good luck!!!
