Hey Praveen, Go to Chennai as you have only one day ... marine drive and museum is worth a visit ... if you have little more time roamed around Chennai and enjoy night life ... Happy Travelling Bro!!!
Travelling 320 km will take most of the time for Pondicherry..
Not sure about Chennai attractions... if you plan for Pondi, look for train options(its available from Bangalore) during night and enjoy there in day time.