Understand bandwidth terminology
"Almost every 200Mb/s adaptor uses a 10/100 Ethernet port, capping the throughput at 100Mb/s."
100baseT and 1000baseT ethernet is full duplex. This means you get 100/1000 Mb/s in each direction, and thus double that in total. In contrast wireless and powerline figures are quoted as total bandwidth. Thus a 100Mb/s port can carry the 200 Mb/s of which such a powerline adaptor is capable.
I'll be sticking with my CAT6 cabling giving me 2000 Mb/s (in wireless / powerline) terminology. :-)