I would always advise taking a course in real space where possible. It's from i-to-i, who are well-known, so many would know of the course, but there are many stories going around about online courses. Yopu can look here for jobs in China:
While heading to China is likely to be an amazing experience, I would still recommend checking out a scool carefully- it isn't just a question of money. There are some very dodgy schools out there and things can go very nastily wrong, so check any place out and look at the ESL blacklists to see if anyone has had a bad experience. I live in Asia and have had a wonderful time and found it a very enriching experience, but there are many cases of it turning into a nightmare.
(Feel free to contact me by private message if you want to ask about places- I haven't worked in China, but I do know people who are there and could help.)