Research is research. Any research is better than no research. You can be involved with Epidemiological studies which also fall under the umbrella of Clinical Research. I think PDs care more about whether you have learned to gather data, evaluate data, and draw conclusions from these data than the specific area you explored. Whether it's a PH environment or basic research or clinical research environment, the process of 1) setting hypothesis, 2) selecting methodology, 3) collecting data, 4) evaluating data, and 5) making conclusions based on data remains the same.
Nevertheless, if you plan to apply to competitive specialties, it helps to have completed research in your area of interest.
One key difference I have noticed is that it's heck of a lot easier to get published in clinical research than bench research. One could work for years in bench level research without publishing anything, while you could tag your name along with other researchers on a clinical paper for example, way more easily if you make the right connections. I think PDs recognize this as well.