RG3's completion % is higher cuz they throw a lot more screens and swing passes. Luck runs a more conventional, down field passing offense. RG3's yards per pass is where it is cuz of his WR's yac and since they've ran so many screens it's opened up the deep ball on occasion and he's hit a few big plays.
But if you were to compare how many targets Luck has thrown 15+ yards down the field compared to RG3, I'd be my Lamborghini that I don't own that Luck has far more attempts in that category.
RG3 is a freakin' man beast, no doubt. But Luck is the better QB.