On paper Scorpio is going to be more closer to a generational difference in power between its predecessor, whereas PS4 Pro is much closer to the PS4. Of course, the PS4 was more powerful anyway, but if both manufacturers are heading in this direction then Microsoft's way of introducing a console that is more significantly powerful makes more sense to me. I feel like at the point it launches we might desperately be craving a more powerful console, whereas that doesn't seem to be the case with the PS4 which still seems to have plenty of untapped power.
I like the idea of the PS4 Pro, I'm just not convinced they've committed to it and introduced a console that is truly capable of delivering what it should. Scorpio seems better in that regard, but then we might have the PS4 Pro 2 coming along a year after that so it could be a case of constant oneupmanship going forwad.