Verified answer

i don't know all the companies so:

Oldest: SM Entertainment -- they have been promoting since the 90's.

Best:

- popularity - SM

- tactic - SM

- idol fee - YG

Accepts International trainees:

- SM - they have been letting Chinese into their company; but actually they have trained Japanese, and other nationalities too but only Chinese get into it so far. Then according to a blog (I forgot), there are Malaysian trainees and other SEAsians trainees in SM now.

- JYP - so far they have few Thai idols like Nichkhun, and Chinese idols too.

- YG - some people say they train foreigners too.

oldest Is SM to YG and JYP

Best is YG, since they make a big BOOM in this planet with Gangnam Style and BIG BANG

Next is SM, then JYP

International trainees? JYP then

JYP Had Thai (Nichkhun), China (Fei, Jia)

SM, had China (Victoria, Chen)