Virgin over World Traveller: every time
I fly Virgin Premium Economy on any long haul flight where it is an option. The first time I flew Premium it was because I needed the leg room following a back injury, but since then I have been able to fly in this class consistently, often thanks to the additional frequent flyer points you accumulate in this class and which I have used to upgrade from Economy.
I have flown BA World Traveller on one return London to Cape Town flight.
There certainly was a difference. I felt cheated, having expected something on the lines of Virgin Premium Economy. I will never willingly fly World Traveller again. The only advantage was additional legroom compared with Economy. (There's no separate, rapid checkin; no welcome bubbly, nothing to match Virgin's ergonomic new Premium Economy seats and entertainment; nor did it match Virgin's onboard service and its catering.
There is one more thing. I'm not someone who asks for, dresses for, or gets upgrades. Except on Virgin. I reckon that I have been upgraded on at least 25% of the flights I have taken with them and on only one flight with all the other airlines I have flown with.
I hope they thrive.