The PS4 has more powerful hardware than the XBox One. If they are running the same game (The Witcher 3), logic tells us that it will be easier to get fluid framerates with the more powerful console. And that is what you care about, no?
Now I don't know about The Witcher per-se but there have been a good number of multi-platform releases where performance and fluidity were compromised on XBox One.
And it doesn't just seem to be Sony, the numbers say it's Sony (especially in Europe). General consensus is that Microsoft severely botched the launch of the One and has been left to play catch-up since.
As I said; I don't know specifically about The Witcher. I used the name as an example. There will always be additional factors beside hardware power, but in general; more powerful hardware is easier to get good results with.
Now I don't know about The Witcher per-se but there have been a good number of multi-platform releases where performance and fluidity were compromised on XBox One.
And it doesn't just seem to be Sony, the numbers say it's Sony (especially in Europe). General consensus is that Microsoft severely botched the launch of the One and has been left to play catch-up since.