Personally, I think English is better, because English, such as grammar, is dead, there are rules and routines, and besides, it is all language. Chinese and English still have a lot in common, and it is best to control the language physically and psychologically. If you teach math, you should always keep a clear head, otherwise you may be confused by students. Although sometimes teachers are not as normal as students, as a teacher, I really don't want this to happen. So mathematics is still reserved for rational people. In fact, it depends on what kind of person you are, which subject you are suitable for teaching and which subject you are proficient in and interested in. Interest is also very important for teachers. If you are interested in the subject you teach, you will be full of energy and students will learn better. After all, it takes decades to teach. If you are not interested in this subject, you can pass it.