I have done both and as I stated before BA Business is probably the best I have ever been treated.
VS is slipping. I do them every year from the West Coast through London to South Africa. The only difference I see in VS Premium is the seat is a bit bigger. from there on its is economy in the worst fashion........ This year I did Continental Economy and it was better than VS Premium (except for the seat).
I will say that the folks who work the counters at VS have always been very helpful to the point of going the extra mile.
If your going to fly Business do it with an Airline that advertises Business, not Premium Economy.......