I believe both sides used these sights in about the same magnitude in the ETO, and it was in a rather limited fashion. 200 or so German fighters entering combat with the EZ-42 sight.
for the LW that is correct, 5.Sturm/JG 300 first used them in a small quantity for anti bomber use in their Fw 190A-8 and A-8/R2's using the EZ 40/42 on 5 sorties during the time frame of September 13-28th 1944.
the initial use by II.Sturm/JG 300 seems to be in August of 44 via documentation translated
The sight was of great use in the Me-262 because of this aircraft's high speed, the gyro sight helped increase the accuracy of the short bursts fired and also made the Me-262 a lot more capable of deflection shooting when engaging enemy fighters.
it does seem odd the Sturmgruppen and JG 300 instead of JG 3 have them first, it was JG 3 Sturm unit that wore the whites of their eyes not JG 4 or 300
the gyro sight was needed for the newer pilots so they could home in their mg 131's and 2cm weapons onto the tail gunners position otherwise in many cases they could not hit the broad side of a barn.