To make it simple, think about yourself and your skills and your interests. How do you feel about teaching and being a teacher? Let that guide you. Regardless of statistics, I think people are likely to do better, and, ultimately earn more, doing a job they love and are good at.

Teaching and translating are both ordinary, salaried jobs, and most of the people in them are "individual contributors," not managers. Both of them are obviously useful and needed, I'm sure you can make a good living doing either. I doubt that there's a lot of difference in average salary.

I think it must be harder to reach the level of language skill needed to get a job as translator than a teacher, because you can teach someone English, as long as you are a good teacher and know more English than they do.

To be a translator requires a high degree of skill in both languages.

Many big US cities, such as Boston, are multilingual, and places like hospitals have a telephone service on call--with human translators--so that they can communicate with non-English-speaking patients. And there are a fair number of Arabic speakers in our local high school. There must be a demand for Arabic-English and Farsi-English translators, but I don't know what the supply is like.

I am sure that there must be a high and increasing demand for [i]simultaneous interpreters[/i], but that is one of the most difficult and stressful jobs in the world.

Your mother tongue is Farsi, isn't it ? you always start from your mother tongue. If you translate from a difficult language (Chinese, Japanese, even Russian), you'll be better paid than if you translate from English (or French) to Farsi. 

Being a translator is not a bad job. Unlike what is sometimes said, you don't work alone, there are a lot of contacts (or a few, depending...) with your customer, who is keen to have the documents translated. 

Being a teacher is sometimes boring. Not all students, pupils like English, or German. If you like your pupils, maybe teaching is less of a burden. It depends on you. 

Speaking about translation, you should probably think more about INTERPRETING. These people are very well paid, but the studies are extremely difficult. 

Just written English translation is hardly needed ... 

Hope I could be of some help.