I was on BA WTP a couple of weeks ago YVR/LHR and yes you do get champagne on boarding. In service terms I would rate BA and VS pretty comparable though I think on balance BA is more consistent. Last flight on BA the cabin manager in WTP ( Sophie) was not just good she was brilliant!
We mostly fly to YVR and BDS, always choose BA 747 on YVR as the timings are better. On BDS choose VS as I really don't like the 777.
In your shoes I would probably be flying VS on aircraft choice alone and for no other reason!