I've done both VS and CO on this route in economy and I'd take the VS product (and I am Platinum Elite on CO). Everything that already has been said is true: the AVOD is excellent, the food is decent, the drinks are free, and the crew is top-notch. For VS flights, I get to the airport early and snag an exit-row seat (31B is my favorite) on the A340-600 for 100USD/50GBP. Miles of legroom!