You should do both. Unless you're interested in contributing to the space of statistical methods and data science research (e.g. developing better algorithms, proving optimality, etc) most people are interested in applying data science. Applied data science is more than just knowing methods and techniques, it requires deeply understanding the domain specificities and nuances of the problems you're trying to solve.
So if you're interested in clinical medicine which has many substantive research areas, you should study that and take quantitative methodology and data science classes along side it. There are many interesting spaces in in medicine and biology that apply data science.