I have had the luxury of having both ART and Graston performed and have to say that you can't really go wrong with either or. I am a Certified Athletic Trainer and actually just finished the Module 1 course and am now competent in Graston. I plan on taking Module 2 to become "Graston Certified" as well. I know it wasn't asked, but I'm sure some people are wondering which is better, ART or Graston. It is really difficult to say which is better since they both provide benefits to patients. I will say that from my experience as a patient of Graston/ART and as a Graston practitioner, Graston will be able to cover a larger area with greater ease, but the ART can be more spot specific with its treatment. Not to say that Graston can't be spot specific or ART can't cover a larger area, but generally it easier for Graston to cover a larger area. Also, there are just some areas that the Graston tools are just uncomfortable for treatment, but a thumb works great with ART. Each has their positives and negatives, but both give great results.
I do agree with what BBB said in that some Graston/ART practitioners are only good at that one thing, but this is why you find a great all around practitioner, not just any Graston/ART practitioner. I find the best practitioners combine a mixture of both hands on and tool treatment. When I took the course, we were actually taught some hands on techniques to include with our Graston Tool treatment. Generally, if you go to a therapist who is only hooking you up to stim or giving you ultrasound, giving a quick stretch and sending you on your way, or just giving a Graston/ART treatment and not following it up with anything, you need to find another therapist. Graston/ART will work best when combined with ROM work, rehab/muscle activation work, and proper exercises for restoration to tissue tensile strength, length, etc.
Sorry for the rant and length of the post but I hope it helped. Definitely willing to answer any other questions people have.