Most employers in Taiwan don’t know the difference and doing any TEFL course won’t really affect your income. However, if you are ever planning to work in Europe or in certain international organisations, you should plan to do the CELTA or the Trinity cert. as a baseline qualification. If you don’t do it because you think you don’t need to at this point of time, maybe you could be ruling out certain jobs in other countries, later on in your career.
Whatever you decide to do, try to make sure the course has a significant element of observed teaching in it, otherwise you might as well just read a book. Bear in mind that a course which isn’t particularly demanding isn’t really preparing you for much.
In terms of applying for a job, employers want flexibility, energy and the personal qualities that put bums on seats. They are unlikely to give you a test, but demos are common. Usually, you deliver a 20 minute mini-lesson and they judge you on whatever criteria pops into their teeny little boss minds. (It’s illegal for most non-Taiwanese to do these, yet the practice continues.). Bosses don’t want you to simply teach English, she/he wants you make money for her/him by selling English learning. It’s an important distinction to grasp in order to be successful and happy teaching English.