There were other differences as well. In this case, AMC-14 will be in a controlled re-entry. The spy satellite had lost all power with no way to steer it and would have been in an uncontrolled re-entry. Also, the fuel in the spy satellite was frozen into a solid block due to the loss of power. One of the fears was that the fuel would survive re-entry and then thaw out in the atmosphere and be dispersed over a wide area. Not a good idea to spread hydrazine over a wide area.The reason that one was shot down was because it was a SPY Satellite and had highly classified spy technology on board.
To me that was the reason why they blew it up.
Now a communications satellite on the other hand, there is nothing top secret on it chances are it will burn up in reentry. If it don't then still no secrets gained by whoever finds what is left of it.