Stronger speed drop as WLAN

In my current network with a normal number of consumers initially succeeded in coupling the two devices hardly. After a successful setup, I was extremely disappointed by the unfulfilled hope of trouble and lossless fast connection. We have VDSL 50 (51 392 kbit / s). A comparison measurement between wireless and powerline proceeded as follows:
The Powerline I put into different outlets with different distances to the router (or the power strip). At these points, I measured the speed on the Powerline one hand, and the WLAN (laptop own wireless card) on the other. To my amazement the speed over Powerline fell from more than WLAN.
For better dLAN connection (Powerline), the manual suggested to pull test, certain consumers from the power outlet. Often business devices such as washing machine, refrigerator and electric stove not come into question for it.
In general, I am disappointed, but should dLAN provide interference-resistant and faster alternative to Wi-Fi. Our house has 3 floors and really thick walls, although the WiFi was faster. Unfortunately, only 2 stars.