Is it best to use KrisFlyer or Velocity on booked flights?

[Flyinfish]

Have just booked return flights Singapore to Rome for May next year with SA.
Is it better to join KrisFlyer? I'm Velocity Silver now so no perks and not using Virgin much anymore. Plan to purchase a one way to Singapore with Scoot as well.

 

[Brizz]

KrisFlyer gets you free WIFI for the trip - Velocity gets you points and SC's