Celta or other TESOL??

The trouble with your question is that nobody has taken two courses! I did the CELTA and it was excellent... I am currently doing my teacher certification (Secondary Language Arts) and in all honesty I refer more to what I learned during the CELTA than what I did on campus as part of my degree program. However, I do suggest you check out the link below and throw some feelers out about the center you plan to do it at (or better yet, the specific teachers who are going to be running your course...). I had one amazing teacher (Bjarne Vonsild) and another horrible teacher (whose name I won't mention out of fear of retribution!).

I highly recommend doing the training in the country where you want to teach. This is sooo helpful in terms of making contacts and friends right from the start, and it's a lot easier to find a job. If you don't want to stay in Korea, consider doing your training elsewhere. I did it through IH Barcelona and it's an AMAZING facility... it's not new or anything but the support staff are fantastic and there are great resources at your disposal. Of course, I have dual citizenship so I was able to work in Europe!