big ca firm--what to choose

Hi to all the C.A. fraternity.

Actually i'm a bit confused regarding gettin in aBig Chartered Firm.
I've heard that I'll have to choose a particular field like either--

Auditing Deptt.
Taxation Deptt.

Is It really so?????

If yes which one would be promising as i wanted to join an industry after completing course.
Practice is not in my mind

Also can change the chosen deptt. during my articleship.

Please reply .