In theory, the VDSL speeds are meant to range between 15-70 Mbps download and 5-10 Mbps upload, compared with the Fibre 30 which is up to 30 Mbps down and 10 Mbps up. This would seem to indicate that switching would be a sideways step at best, and a potential downgrade at worst.
I don't think we ever get close to 30 Mbps download speed, but I don't test it very often. My gut instinct says that the Fibre plan should sit closer to 30 and also be more reliably fast than VDSL is, plus changing to fibre will allow a much easier switch to faster speeds at some point in the future.
Any thoughts would be appreciated, thanks.