Rob,
We use light speed Zulu headsets in the 912 powered skyfox and have found them to be the pick of the various combinations I have tried to date. Have used lower end altronics & telex passive sets, as well as an early retrofit version of an anr conversion in the altronics headset. This was ok, but not nearly as good as the light speed Zulu.
In my opinion in the skyfox at least, you are correct about the Zulu passive noise level reduction, without the anr activated maybe not as good as some other headsets. I haven't tried the bose headsets so can't comment. Over all I am very happy with the overall fit, comfort and operation of the zulu. Take note of the low battery indicator and keep the batteries up to it which I don't believe to be excessive & there are no problems. Sounds like You need to make a trip north and come for a ride & check for yourself!