Many practices employ injectors (Nurses, cosmeticians etc) to inject Botox / Juvederm / Restylane / Perlane etc. Some of these injectors are good, many are average and some - well we won't go there.
I personally believe there is no substitute for excellence and specialization. Just as you should see a Cardiologist, not a Gynecologist or Family Practitioner, for Heart disease and a BMW mechanic, not a GM mechanic, for any BMW issues, you should seek the best when it comes to Injectables.
I firmly believe that Plastic Surgeons have better knowledge and appreciation of the structural Anatomy than non-physicians and therefore would get you better results.
In my practice, I prefer to personally administer all fillers and Botox. I like interacting with my patients and I know my results are better.
Dr. P. Aldea