Nikon DL24-500 is not available yet, so nobody can do a comparison for you. Even the Sony is not widely available, even though I have held one couple of months ago. Seriously thinking about getting one (Sony, that is, "for my wife"), as a f/4 600mm (equivalence) at $1600 is quite amazing, and the image quality is supposedly more than good enough. Nikon D5 with 600mm f/4 costs $18000 and weighs a ton, and the image quality certainly is not 10 times better, not even twice...