DPReview member oracle82 writes:
And the award for most confusing answer goes to Christof21 who supplied the link to a website called How Much Blur, which compares the theoretical percentage of blur captured by both lenses at similar distances.
But the question specifically addressed the separation of subject and background at different camera to subject distances. In other words, supplying a link, no matter how erudite it may seem, isn't enough. Relevance is key.
The best response from the same thread attempts to answer the question asked, which distilled simply is this:
I like to shoot [people or other objects] at wider angles. Because of this I have to move farther from my subject when using the 35mm 1,4, which reduces the amount of separation between the subject and the background. Which lens, the 23mm 1,4 or the 35mm 1,4, would return more separation between the subject and the background?
The answer lies in the oracle82's own question: Of course, then I start to lose some of the blurred background because my subject ends up being further away from me.
Any answer concerned with the amount to which a background is blurred and not the degree to which the subject and the background are delineated one from another, is pointless. And so becomes the 35mm's f/1,4 aperture when the subject is moved closer to the background in order to capture a wider view.
The answer is: no, you are not.
The 23mm 1,4 lens will more keenly separate the background from the subject.
Here is the thread: Am I wrong in thinking I could get MORE subject separation with 23 vs 35?