Our fullbacks are playmakers- and very few teams have fullbacks like ours. Trent will continue in the fullback position, and together with Andy, will change how fullbacks are viewed in the modern game.
Kids will grow up wanting to be like Trent or Robbo- the best fullback playmakers in the world
Robbo is brilliant going forwards, but you can't usually give him the ball and say 'make shit happen'. If somebody else has the opportunity to create something, Robbo will always make the run to enable it, he'll supplement that creator, play the accurate final ball, make the right decision etc. And he'll do it very well, to a standard better than (nearly?) every fullback in the league.
Trent, you can give the ball anywhere and he will make that shit happen of his own accord. He'll cut inside and play a 40 yard chip to the edge of the 6 yard box, with his weaker foot. He'll bypass the midfield press and find you in acres of space, or find your sprints in the channel. He'll pop free kicks in the top corner, he'll dribble around the press, he'll play 70 yard diagonals.
Robertson is the prototypical fullback, but Trent's the true playmaker that you're referring to. Like Dani Alves and David Alaba, Trent is a CM/CAM playing fullback. Robbo is more like Abidal or Jordi Alba, 'merely' a fullback doing his job to the highest level. Just my opinion anyway