There is also a huge difference in antenna performance and between different receivers, which may also colour the results of their tests.
The simple suction-cup antenna of the portable Garmin GPS 196 cannot see through the thick front window glass of a UH-1H or the heated glass of an S-76, but gets perfect reception when we put it in (of all places!) the chin bubble. This set will now lock onto the constellation well before the built-in Garmin or the UNS-1K.
Two blades or four blades don't seem to affect it.