Also being a VS Flying Club member, the main difference in VS’s favour for me is on the ground and in the air consistency and staff brand awareness, especially on board. VS staff seem to have a sense of loyalty towards their brand, too. I do not think BA’s staffing model (crews doing shorthaul and longhaul) helps given its network complexity- not least as BA crews often (and rightly?) look fed up and tired but there are always exceptions and some go out of their way.
If BA could get a grip on consistency and ensuring their staff are brand aware (rather than passengers telling them what the service routine or ticketing rules are) BA could gain back its edge a bit.