I am not really qualified to comment as I have only flown for easy but what a great position you are in. In my opinion BA can only decline in terms of pilot lifestyle and terms and conditions and the workforce of late is increasing exponentially. The scale of this is anyone's guess over 30 years.
Virgin Atlantic seems cool but it is as big a risk in this career as any I'd have thought.
I dont think easy will have A319s and 320s for the whole of the next 30 years - that combined with the chance to train, examine or go part time combined with another business give the scope for variety in the future.
Ill conclude by saying that I don't think 2012 will be a comfortable year for anyone at the bottom of an airlines pilot seniority list and virgin would be one of the least comfortable in my opinion. The fact you are even considering speaks volumes. That said I don't think anyone from my era would be a pilot if they chose the least risk, sensible option and now on the other side of my choice I really enjoy my career. Good luck with your choice.