Years ago my master socket was under my desk, so I ran a 0.5M cable to the router then a 0.5M cable to the PC (the router sat on the PC).
Nowadays my master socket is downstairs arcoss the house, so I got a faceplate with built in extension wiring, and ran a Cat6
20M cable up through the wall, through the loft and down again to an extension port, then just repeated the setup in the old house.
Just as good a connection. My point is that in small distances (under 30 metres) as long as the cables and good, the connections are good and with the fewest joint in the system as possible, you probably can't go wrong. It's not as if there's a better choice in that scenario.
What I would start with is plug a short cable from the socket to the router and the same again to the PC (move it temporarily if you can) and see what speeds you get by plugging directly into the back of the master socket. Then start working away from that. If you have decent kit, and you're not running very long cables, the differences will be negligible.