There is no competition when it comes to them. Their movies are of equal footing.
The movie Kris was in (xXx) was filmed recently, like only a few months. My personal opinion is that a Chinese studio helped with the budget and that's why you see chinese actors in this movie.
The Great Wall, which was filmed nearly TWO YEARS AGO. (filming began March 2015)
Now I have no idea why it took so long to premier, opened in China in December 2016 and then in the U.S. February 2017, but I think it might have been due to special effects and hard work they put into it during post production.
Anyway, the point...
No one should complain about Luhan's role being small. When this movie was filmed, he just left EXO, he was just starting his solo career, he had only filmed a couple other movies in China at the time. Whereas, Kris filmed xXx as his career is hitting a new height in these past few months.
So keep in mind, there's a huge, huge time difference. They're not trying to out do each other and there is NO COMPETITION.