I haven't really worked it out scientifically, but I get around 50% of the aircraft in MyFlights with full ADS-B here in the West Midlands of the UK. What I am seeing though is more GA traffic with Mode S transponders, so that is distorting my average a bit, but overall, it must represent more airline traffic with full ADS-B.
Only my opinion of course ........... ;-)
I'm using the BS1100 external antenna with about 10 metres of cable - can't see any markings on it, so nothing special I guess.
Report for today attached if you are interested - 1072 aircraft so far