Tata Sky logo is best for following reasons:
1. It has the smallest logo among all DTH.
2. It shows extra small logo on HD channels which is so small that almost disappears sometimes.
On 2nd number, I'll put Videocon D2H logo and on 3rd Dish TV. Airtel logo is very big in size and not very transparent which looks very odd and annoying on channels. If they remove the background color and make the logo more transparent and small in size, it would be a lot better. And there is no word in this world for Sun Direct's super huge logo.