It seems that different forums are dominated by the patients from different doctors. You can find numerous reviews from Dr Cinik on the realself.com.
I've spent several months doing my research looking at the two. Both Dr. Erdogan and Dr. Cinik provide very good quality work, and customer service. If I am not wrong, Dr. Erdogan's clinic offers manual grafts extraction. Dr Diep's work is also great, but I could not afford it.
Due to financial constraint, I decided to go with Dr. Cinik.