With regards to pressures, really?
My perception and experience seems to favour lower pressures with stiff tires and higher pressures with softer tyre construction. With Bridgestone, Pirelli, Metzler etc I would be running 32/34-6 norm street and 32/30 - 2 hard riding. Cold temps. I found the tyres tend to walk on me if I have the pressures higher and that is not fun especially on the front end when pushing them. Higher pressures for soft carcass sidewall tyres to help them retain shape under stress.
Love the Bridgestone S21's and interesting to hear your thoughts about the new Michelins.
I was out today on the S21's 2 to 5 degrees C with some snow flakes and rain on the ride, slightly cool but fun to be back in the saddle. I like the aspect of being able to correct my line mid corner on them as on the street which is most of my riding, you never know what surprise might crop up. The Michelins sound though like a lovely track tire or at least corner carver where you know the route like the back of your hand and know the surface to be in good order.