I have no experience with the Zulu's or the Pilot USA headsets, but I have been flying with the DC X11's for the last year.
The X11 headset is the most comfortable on my head, even more so than the Bose X. Six hour cross country flights have no discomfort from the headset. The noise canceling is great, and it seems to be very durable for being mostly plastic.
I do have two complaints about the DC however. First, at my current job (instructing) I am in and out of 3-6 different planes per day, flying usually 5-7 hours daily, and the batteries don't seem to ever last more than 3 days, no more than 20 hours of use.
And Second, the X11 is a quiet headset. Not only in noise canceling, but in volume. I always have the volume all of the way up on the headset, and have to warn my students to turn theres down so i can turn up the volume on the radios. This is a problem i have spoken to other X11 owners about, and seems fairly common, (and no I am not losing my hearing).
Have your considered the Bose QC2/Uflymike combo? That is the direction I am currently heading...