The key would be the decision making.
Time of the game (early, late, etc.), state of the game (did we just score / looking to close out the game, etc.), who's the fullback, etc. cost vs reward
If he's coming up against a Jayden Campbell... he's short, doesn't really jump for the ball and when he catches it he usually drops straight to the ground to avoid getting belted... perfect candidate for Riki to compete for the ball.
However, if he's up against a Gutho then just focus on wrapping him up and defending. Gutho is good under the high ball and good catching it under pressure... He can also punish you if you miss your mark and over run it.
In the first half of Game 2 Hammer and Taulagi were getting to To'o on the kicks and he had no support or blockers around him so he was primed for competing on kicks, but the Qld'ers were just looking to tackle him and complete the play. In the second half they completely changed that and started competing on pretty much every kick those two could get to... so it would seem that Billy spotted it and got his guys to change tactics.
If you drop a kick that you can get to cleanly and compete for then it's only going to cost you a knock on and changeover (assuming it's 10-30m out), which would be the case anyway... so there's no real negative to just competing for it and hoping to get it cleanly or force an error from the winger/fullback... more teams should be doing it really.