Although it is still possible to find a position teaching English abroad without an English teaching certificate, most employers look favorably on such credentials (and most instructors find that they give them a leg up on the increasingly stiff competition). Still, knowing you need a certification does little to answer the question “which English teaching certificate is right for me?”
This is a question that is easier asked than answered. After all, while it is true that – to put it simply – the more training you have the more opportunities will be open to you, this is an issue that defies quick conclusions. Indeed, a MA in TESOL would put you at the top of the pack but may not be appropriate for someone who is just entering the field. Indeed, because longer courses require a greater investment of time, energy, and effort, they are a better fit for those who have decided teaching abroad is a long-term career.
More to the point, it is important to remember that many international employers look favorably on short TEFL courses – and many training programs offer employment services designed to match graduates with exactly those employers. Because they are quicker, simpler, and easier to obtain, TEFL certifications – and even four-week CELTA programs – are a good idea for those who are just starting out in international English education.
International, however, is an important word here. Because a DELTA or MA in TESOL are often viewed as prerequisites for positions at colleges and universities in North America, those who are interested in working domestic would be poorly served by standard 100 or 120 hour TEFL certifications.
In the end, the biggest factor you should consider is your potential employer. Depending on the location or position you have in mind, you should research the different options available in order to determine which one will provide you with the biggest advantage in your particular job search.