One of the many unique features of service in Korea (like curfew and alcoholism) is the KATUSA program. There are usually 2-3 KATUSAs per platoon, and while I don't want to exaggerate their abilities, I can say that there is usually an embarrassing disparity between the KATUSAs in my battalion and the US soldiers they serve alongside. Regulated by their company's "Senior KATUSA," the battalion ROKA Sergeant Major, and weekly, secretive "KATUSA meetings," (where, perhaps, the Sergeant Major threatens to beat them) they are incredibly respectful, never have disciplinary problems, and score high on their APFT. They are successful machine gunners, clerks, team leaders, Bradley gunners, you name it.
This is not to suggest that a Korean makes a better soldier than an American. However, our Koreans often do, because they already went through a few selection processes. To be a KATUSA you have to win a lottery, though to compete in that you have to speak English fairly well, which probably means your family had money for English lessons and you have started university. Then, to be an infantry (possibly all combat arms) KATUSA, you have to volunteer again. So while the average ROKA draftee is nothing impressive, the guys who make it to us had to do a bit more than walk into their recruiting station and pass the ASVAB.
I haven't noticed this during joint exercises, but supposedly in the "old days" (somewhere between the establishment of the DMZ and the end of the $20 blowjobs outside the front gate) normal ROK soldiers would beat up KATUSAs whenever they saw them because of how much better off they had it with the Americans.
*Yes, the glasses really are that big. And they do only get issued one pair of boots for their two years in the Army!