Surprised that people who live by Victoria would still choose LHR. Almost seems that LGW is a no brainer for the South Hyde Park area.
At the end of the day A350 / 77W doesn't matter for me.
What matters is the arriving airport. If i need a shower on arrival, then I will choose LHR. Otherwise, I actually find LGW to be very efficient around the time that CX arrives (no queues at immi especially if you are the first few off the plane at immigration).