Signal Quality is most important and to be precise need check Bit Error Rate (BER)
I feel for DVB-S2, ideally we should target to achieve the BER of E-10.
I was getting BER about E-04 level and was having a picture quality bad i.e. blurry on my AirTel HDR noticeable on SD channels like Zee & Sam.
Later we have reposition the DISH and then further gone for two different DISH for each Tuner of the HDR so that the drop with both Tuner simultaneously working has vanished.
Now I am getting T1 for E-08 to E-09 and the other is E-06 to E-07, the picture quality is feel ably improved on SAMSUNG 51E8000.
Still working on other Tuner2 to improve it further.
Normally people says that in Digital Signals there is no PQ difference once you get minimum Signal strength required for Display, but it is not True.
We need to achieve Quasi Error Free Level (i.e. BER below E-10 for DVB-S2) to get Better Quality Picture which is called as Perfect in digital terms i.e. FEC (Forward Error Correction) logarithms can compensate for a certain amount of errors to produce "perfect" picture.