What about connecting through LHR on BA or VS? Though, as an East coastman, I'm not sure if that would be longer or shorter for you. With your current choices, in terms of service, both are fantastic. I'd probably go with CX for this route just to avoid having to transfer in Mumbai. Mumbai is not Hong Kong and HKG will be much easier and nicer, especially if you have a wait since there's much more to do as in shop or eat or just sit around.