With so much uncertainty at the moment, the best option by far is to keep your points where they are – as credit card points. This gives you maximum flexibility and ensures that your points won’t be wasted.
If you really, really must cancel the cards now and dump the points somewhere, my vote in the current atmosphere would be KrisFlyer. While it’s almost certain that Velocity will survive and thrive into the future, there’s just that tiny bit of uncertainty at the moment while Virgin remains in Administration.
The major downside of transferring to KrisFlyer is that your points will expire in three years once you’ve transferred them. If you’re willing to live with that, then my vote would be KrisFlyer.