Those 2 were also my candidate schools for master degree a while ago. So I did my research back then.
Stern has a great reputation as business school and its location will help you get a job easily after graduation.
Carnegie also has a great faculty, curriculum and reputation.
If you get financial aid from Carnegie, that would be my first choice.
In case you go back to Korea after graduation, Carnegie’s reputation is as good as Stern in Korea. People know.