Ponga is just a truly exceptional player and this video only further accentuates that fact.
Although he is going to league (and staying for the moment), he would be, in my opinion, far more effective in union. League is effectively a line of defenders and set play off every tackle, whereas union creates much more open space through more free play that opens opportunities to roam through the field as is shown in this video.
wait until you see him play rugby league then... you would be suprised