I don't think there is a thread. I have stayed at both. Both have ski-in/ski-out and very nice onsen facilities. The PH is quite a lot bigger, the Ritz is more intimate.

If you can get a suite at the PH that is in the residence section you can get a private onsen, not entirely sure if any rooms at the Ritz has private onsen.

There are more inhouse dining options at the PH. But the Ritz is probably closer to other dining options, but as you anyway probably have a car, nothing is too far away anyway.

Probably a bit of a toss between the two in my view, but it depends on what you focus on from the hotel.