This is totally going to come down to your flying patterns.
Firstly, if you are flying business and will eventually spend SGD$25k, forget Gold and wait for PPS to land.
If you plan on doing a lot of flying with Singapore and can use the miles for upgrades etc, then they are better there than Velocity, due to the 25% devaluation when transferring them. Since you are already Velocity Platinum, there are no additional benefits to be had here.
If you plan on doing a lot of flying with other Star Alliance partners other than Singapore (or Air New Zealand to NZ), then there may be some benefit in this, but it’s limited. Air China and United spring to mind, however.
If your partner regularly flies without you, however, and you have already RENEWED Platinum in this year, then gifting the Gold will probably get you more rewards than either of the two above.
For what it’s worth, I did the partner Gold last year when faced with that decision, then used family pooling to make sure it also renewed for another year.