The only answer to the question posed by DPReview forum member, labe, is excellent; although The Davinator's reply is pretty much spot on:
“The D610 is going to be a solid two stops better at high iso. That said, I’ve used the X-Pro1 at 6400 iso during wedding receptions and produced wonderful 8x10 and 11x14 prints for album work. As good as the Nikon for noise....nope. But the Fuji WB and color spanks the Nikon.”