I think it really depends on the school. Ideally, it would be best to have both clinical experience and research, however, if I had to pick what was most important, I would probably say clinical experience. This is pretty much a necessary component to get in for the most part. But if your applying to schools that are major research universities then I would say that research experience is very important. For me, at my state school, clinical experience is absolutely essential and they won't even look at you seriously unless you have some quality experience (from what I've heard).
Hope this is helpful! 😀