I would note that it does also depend on where you want to go with your points. If you're looking to get to Europe a lot, then with VFF you'll have QR and SQ, along with EY in Y (J is restricted to 30 days) - even technically NH, although availability is limited. If you're looking to fly to the USA, then you have United which has been patchy, and AC which has been nearly non-existent in J. If you're looking to fly within Asia, then you'll pretty much be always routed via Singapore. So availability is a lot better with VA, having access to QR and SQ, both of whom have excellent networks, but you have less partners overall, so specific destinations might be a little more difficult to get to, or they just might require a stop. Hopefully VA keep improving this!
Also be aware that IMO Velocity status is less valuable than QF status, purely due to the lack of alliance-wide recognition when travelling. This generally doesn't matter if you're travelling on award J tickets, but in general the lounge access policy flying partners using VA status is more restrictive than flying partners with QF status.