The best way for me to explain the difference between the two in my opinion.
I sit in Colin Bell lower, Isle/block 130. When Silva is playing, you can see a total difference in the game. If Hart, a full back, centre back or Ya Ya have the ball they look for the space between midfield, central defence and their full back. Silva will sprint into this space, take the ball either in space or with a man on. He will then dictate play for a period. He will use our full back, Ya Ya, Sergio a wide man to create more space higher up field. He will then use this space to play in a full back or a De Bruyne or Navas, in turn they will play the pass that creates the chance or block in Navas's case;-).
This pattern will be repeated on both sides of the pitch, continually Silva will drop, revived the ball, turn, gain ten yards with the help of 3 or 4. Push the opposition back, he will then look to use runners who create the chance or if there's space he will play the killer ball. Sergio and him are terrific together.
Contrast this with De Bruyne in his City career to date. De Bruyne doesn't want the ball with his back to goal. He doesn't want to build up play slowly and push teams back with triangles using the team, these are not his attributes. In my opinion De Bruyne likes a Silva like player to deliver him the ball, allowing him to play a quick one touch pass, often a dangerous or creative pass. For me, De Bruyne doesn't want to keep the ball, gain ground through possession he wants to kill with possession. Not saying he can't keep possession but he is not suited to the role of play maker. He doesn't suit taking the ball in tight spaces, he doesn't want the Barry's of this World nipping at his ankles just so he can gain ten yards, he wants the ball in front of him, so he can play his killer ball, try his killer cross/through ball. This is not a fault, this is an attribute.
For me Silva, Ozil or Fabregas are play makers, they use the whole pitch to dictate the game. They are as happy deep as on the edge of the box. The games runs through them. They are unselfish, take the fouls, foul themselves all to help the team tick.
In contrast is see De Bruyne more of a Hazard, a Sanchez a player 100% capable of creating from advanced position, beating a man and capable of both individually brilliant goals and assists. I don't see them totally comfortable recieving the ball deep, creating. I see them as players with the brilliance to effect any game at any point. For this they need a play maker alongside them.