An alternative option should be to join both schemes and evaluate which one has be better points generating power.
For me, Virgin will have to make some major in-roads in the CC market to be able to do this. as Virgin already has a CC this will be an issue when they want to co-brand with another CC company.
Customer loyalty can be pushed around a lot (as seen with Qantas) but I find that the benefits of having multiple channels of earning points and the hassle of changing CC's will stick me in the Qantas side for now.
Give VB a few years and more strategic alliances and I'll seriously consider it.
Regards
Daniel