Who is more qualified to do my liposuction: dermatologic surgeon or plastic surgeon?

You have asked a loaded question and from your experience, you can see that there are "turf" battles in medicine and surgery.   There is no doubt that your board certified plastic surgeon is more qualified to perform your liposuction.  Why?  Because we know how to operate on the entire human body, from the skeleton, muscle, fat, skin, and just about everything in between.  Plastic surgeons can treat the human body as a 3-dimensional structure and dermatologists treat the skin in 2-dimensions.   The plastic surgeon has the technical know-how and experience to build the "house" from the ground up, not just "paint" it.   Most importantly, it is the plastic surgeon who will know how to "fix" your issues should there be a problem or complication.     

There is a lot of misinformation out there about liposuction but the important thing to keep in mind is that it is surgery. Even though the skin incisions are tiny, the volume of tissue affected can be large, just like any other surgical procedure. When people emphasize the safety of tumescent technique, which is popular among dermatologists, they compare to old data about general anesthesia. However, most procedures are probably done with monitored intravenous sedation and some version of tumescent, so it's a false argument. What's more, there is the potential for lidocaine toxicity when trying to do too much under tumescent so the safety question ultimately comes down to the judgment of the surgeon and whether or not the procedure is being done in anaccredited surgical facility.