Having C-17 side by side with the Y-20, one can really see the difference and design philosophy.
For example, the Soloviev D-30KP-2 on the Y-20 is much smaller in diameter compare to Pratt & Whitney F117-PW-100 on C-17 - the F-117 is both wider in diameter but shorter in length; the Y-20 has a much bigger hump on the top side (and not as smooth transition) compare to C-17 making C-17 having a flatter profile; the nose cone of Y-20 is shaped more like a "bird's beak" pointing downwards than C-17's centerline approach; and then there is the obvious winglets that's missing from the Y-20.[/QUOTE
Actually, well probably because I do enjoy being a little contrary at times, I find the Y-20 to be a virtual clone of the C-17 in design philosophy, as you point out differences, those are rather small differences, the engine nacelles being an example, they are the size they are to cowl the engines that are available... as to the (bigger hump) on the Y-20, that is simply because the Chinese aircraft carries the spar carrythrough externally rather that having it pass through the fuselage, the carry through is likely bolted to external attach points that are then "faired in", a good design feature given that the "wing box gets lots of torque and the load of both wings is concentrated in that box, making it much easier to change, although I am rather certain it is "draggier" and will increase fuel consumption and reduce airspeed incrementally?