Hi
I have tried researching this topic too and my finding is that Delta airline may be the cheapest.It also has among its options a one and half hour stop at Atlanta which I think will make the journey shorter and more convinient.Flights through Europe have 7-8hrs stopover which can add to jet lag/ fatigue.
I also found out that round trip is cheaper than one way.I dont know why, I thot it should be the other way round.Perhaps somebody can explain this.
So check them out yourself including BA, and KLM,Air France as suggested by Right and post your findings and observations too so we can compare.
@ Right,
Pls what is your timeline?