I'm with SASless, ask your greenie (avionics tech if you are new to this).
Personally, I like the Bose ANR and think they work great, but have used the DC for years and even tried the Peltor (North Sea Specials) that the Scandinavians are keen on - probably for the same reason they like Saabs and Volvos. On an ambulance job where you fly 10 hours a month I wouldn't bother with ANR, but if you're putting in 4-6 hour days I wouldn't be without them. Old S76's tend to be low impedance unless modified in a refit, everything new like a C+ or an S92 uses high-impendence. A reputable employer will offer to replace your microphone on your personal headset if it doesn't match the impedance. The US plug is standard, unless some dufus has changed it. Most new generation avionics, such as AVAD, EGPWS systems etc are all high impedance, making it a PIA for the avionic guys to keep everything working for some luddite's low impedance headset.
malabo