While the CP may offer convenient access to the Shinkansen and trails into the hills, the area immediately around the hotel is sterile. Shin-Osaka is different but also dull. In either city, I'd prefer a "downtown" district over the transit hub as a base for seven days. YMMV.

My advice would be to put the question of where to stay to one side for now and start thinking about which places you want to visit in the Kansai region and beyond. That will inform your choice of transportation (e.g. rail passes https://www.japan-guide.com/e/e2357_kansai.html). When you have a clearer plan in mind, the decision about where to base yourself may become clearer - perhaps you'll choose Osaka or Kobe for seven days, or perhaps you'll find it makes sense to split the time with another city further along the coast, or on the opposite coast, or ....