PhD applications are different that taught Masters or undergrad. The more you know about what you want to specialize in, and why you want a PhD the better. The fit between what you want to do / what you bring to the table and who they are / what areas have grad student funding is way more important than schedule changes in undergrad. You should be able to identify groups within each program whose work aligns with your area of interest, and be able to show why you would be a good addition to that group.
Remember that a PhD is a research degree, so being able to demonstrate that you are able to frame a research question, figure out how to answer it, and then do it is important.