I think Manhoef would do very well against Silva, but I think height and reach would play a huge factor. I see Manhoef throwing alot more and Silva backpeddling alot and tossing those jabs.
Don't forget, Melvin is a short dude. He is 5"8. He aint exactly going to have any easy time getting into range of A. Silva.
I can see Manhoef winning the first round landing a few clean punches and being very aggressive. As A. Silva frustrates him more and more with the reach/height advantage, controls the ring and makes Manhoef work, and starts landing, I can see Manhoef begin to wilt.
I think on a technical level Manhoef has better hands, but with grappling, legs, and the height/reach thing (6 inches is a lot), I see Silva winning.