Just watch some tape between Reyna and Luna. It's not hard to see that Reyna has unique vision and passing that the current roster is lacking
You could argue that Mckennie and Adams are the best passers, but they play center midfield. Gio Reyna is one of our only attacking midfielders that has this sort of high-level "vision." I personally wouldn't start him, but he has more of that x factor skill-wise than Luna. I don't think this "has that dog in him" factor is going to matter much against top players around the world...