Here are my views about both STB:
1. Both Tata Sky and Airtel use same software for their STB, thats why we get similar UI. But Tata Sky UI and EPG looks better than Airtel due to color combination. TS EPG uses blue color while ADTV EPG uses red color.
2. One big drawback and annoying thing with ADTV is the big advertisement bar placed on the top of EPG which hides a little part of program screen. I hate that ad on EPG.
3. ADTV has a bug which automatically deletes some program listing from series recording schedule if the program is not telecastes for a week or more. I have personally faced this bug lots of time.
4. One good thing in ADTV and which is missing in TS is when you see program schedule in the guide, ADTV directly shows selected program's information in the square box shown at the top-right corner of screen. TS uses that square box to show advertisements and we need to press Info button on remote to see the info about the selected program.
5. The biggest annoyance in ADTV is its logo on channels. The logo is bigger compared to TS. Also ADTV logo is not much transparent and looks clearly on all channels. TS uses very small and transparent logo which almost hides on channels.
6. ADTV allows to add only 15 channels in favorites. If you want to add more channels, you'll need to create groups and each group can contain only 15 channels. You can create only 4 groups. On the other hand, TS allows up to 50 channels to be added in favorites.
7. I have also noticed one irritating thing in ADTV. If you change channels quickly, the EPG shows No information available and after 1 second it shows the actual information about the program. So if you are quickly browsing between channels, you need to wait for a moment to check the program information. On TS, the EPG is immediately shown without any delay, so you can quickly browse through channels.