When I was making the same decision a couple of years ago it came down to destinations. Virgin only really seemed to fly west whereas BA went to all points of the compass.
Yeah i think this is where i keep falling down. Maybe it's not as beneficial because i'm not a regular flyer (only a few short trips to Europe each year on Easyjet)
But i'm looking at flights to NY with Avios and in First it's £680/person in taxes and i think alright i'm getting a nice experience but i need to mess around getting to Heathrow which adds a decent chuck of cost on top and then i question if it's even worth it when i could grab a cheap Economy return from Manchester for about half the price!
At least with Virgin, as limited as my options are it's a lot more straight forward!