I wonder if you're still trying to decide which path to choose. I hope I can give you a bit more clarity since I'm a current PA student. Firstly, the amount of time and education required to become a PA vs. a dermatologist is different. I believe a dermatology PA can graduate from an accredited PA school and start working, most likely followed by training and mentoring on the job by a dermatologist. PA students are trained as generalists, so it gives them a great flexibility and versatility in terms of what healthcare settings they can work in.
Dermatologists, as I understand, would finish 4 years of medical school followed by 3 years of residency in dermatology. I believe the average salary for dermatologists is higher than for dermatology PAs, but there's much overlap in what they do on a daily basis. I would encourage you to perhaps talk to at least one dermatology PA and a dermatologist. I hope this helps.