I would say it really depends on what you are looking for from the course. They are both prestigious institutions and highly regarded both within and outside UK. However where KCL focuses on more fundamental and biomedical topics in the first year, QMUL does expand the curriculum in the first year and seeks to cover not only dental topics but also how dental related illness/treatment affects households/communities. QMUL encourages selecting electives from psychology/sociology to deepen this understanding in the first year.