If you want Tamil music channels like Raj music, mega music, sahana then go with tata sky you will all channels get good audio and video clarity. Buy HD settop box you will get good clarity through HDMI cable.
If you don't want those music channels you can select sun direct HD also
I moved due to hevc decoding. Hd channel quality is high in sun direct compared to other dth due to HEVC. Also I think sun direct will provide Dolby atmos sound