You can find the odd good school in Seoul, Daegu and maybe even Pusan, but aside from Universities, the only good reason to teach in Korea is quick cash, as long as you can stand it.
If you are serious about a career in English education, avoid Korea altogether.
Living and teaching in Daegu was for me a great experience because I signed up with a great academy in an upscale neigborhood.
A few years later I returned, this time to Ulsan, and it was HELL!.
Then, in the midst of the Ulsan corruption, lousy working conditions, dishonest hag-won owners, human trafficking of girls from underdeveloped countries and racism, were two Korean sisters, each having bought a Megaton school when this chain (Megaton was a chain) was collapsing, the kindest, most generous people I have ever known. Had it not been for them, I would have died on the streets of Nammok Dong-Gu by leaders of the Ulsan English School Association. One of those sisters checked me into the local hospital, then later checked me out, took me to the supermarket to ensure I would have food at home, and then drove me to the apartment from which I would soon be evicted. As busy as she was, not my boss, she left only after I assured her that I would be OK by myself.
Now back in my country, that generous Megaton owner, is the only reason I don't turn my back on newcomers from Korea who ask for assistance.