Which is a better medium to pursue MBA, English or Tamil?

MBA in English has more scope than Tamil. Most of the multi-national companies hire the students which opt English as a medium. So, you must go for English.

MBA in English medium will give you a better edge on the professional career front. Nowadays most of the organisations prefer hiring candidates with good presentation & communication skills in English.

English medium is the global language spoken all over the world where as Tamil is spoken only in a state or more. If you study English, you will be eligible for international jobs and much more.