I've done LHR-IAD in BA Club World, and flown the route on United (shhh in the back). Purely based on UA in general and having seen the 767 J seats I'd rule them out

I wrote a detailed trip report on the BA experience and took some photos. Sadly I didn't do the return in CW (as you will see in the trip report)

You are right in saying that VS does not operate the new Upper Class Suite on the LHR-IAD route and although I have not flown VS ever (an am unlikely to due to a pathological hate for the 'Ginger One') I'd say this a two horse race between VS and BA.