I'd have to say from my experience that John would be right. My small light kit is a 1K Rifa, a 750W Fresnel and a 250W tota... and with just the fresnel and a reflector I can easily get my XL1s to expose somewhere between f4 and f8 (depending on subjects, contrast range, etc.).

...lens, distance of the light from the subject, type of room, colour of paint on walls, etc., etc. Here we are in a very non-scientific waters.

However, I would (together with most I am sure) like to get a sense of the difference between the HD100 and say PD150 or something most of us are familiar. Some time back I shot some comparison test between the Z1U and my SONY DSR-500 with 20x Fujinon and in daylight under most conditions the speed difference was around 1-1.5 stops at 0 dB. At night it went up to as much as 2 stops. In that test shoot I didn't focus on light sensitivity and therefore don't have the exact numbers but from what I remember, in the mid-range (F5.6-F11) the difference was a tad less and in open wide the Z1U dropped down even more.

Not sure if this makes too much sense but that was my experience. Then again, the exposure latitude is slightly different between those two cameras and so is the sensitivity of their zebra patterns, which might be enough to account for the .5 stop difference.