rhart-The bore axis thing is one item I'll try to quantify when I get a P-10C. Think about it. On a hammer gun, you have to build the frame dimensions around the hammer--allowing room for the hammer to swing. With a striker, you don't need as much room since there is no hammer swing. You have to allow room below the barrel axis for the trigger bar and for the barrel drop and that is about it. I don't think the rails inside/outside make much difference on the actual bore height dimension. The optical illusion is there, as the seam we see is lower in the P-10C than a 75, but the distance from the centerline of the barrel to the top of your wrist may not be affected much. My opinion is that they changed the rails inside/outside to provide more grip area on the slide and to take that concern off the table.
The geometry of the grip is important to me. A very high grip at the rear of the gun with a low bore axis, may not feel right if the trigger pivot is still low in the frame and you have to angle your fingers down to center your trigger finger on the trigger. The more parallel one's trigger finger is to the barrel axis, the more comfortable it is to at least operate the trigger. A manufacturer can lower the grip bore axis a bunch, raise your wrist on the frame, then force the shooter to angle his fingers down to the trigger if the trigger pivot to bore axis dimension isn't also reduced as well.
Everything is a compromise in pistol design. Some compromises work out better than others, depending on the type of shooting and the size/shape of the shooter's hands. Can't wait to see how it works out for us.
Joe