All three sizes I've seen would seem to have their uses. We'll see how the "Popular" works out... I wouldn't be a bit surprised to find that I end up with two, eventually.
Lehman's did confirm that the Large Storm actually holds 50 ounces, if filled to the spout, which they don't recommend. I found more images of these by Googling on "volcano kettle", some are impressively blackened and beaten:
(Also notice the difference in the depth of the bases between these two models)
but a picture or two of the large version gave me a feel for scale, and it is pretty big:
It seems to be an unavoidable compromise with this concept that they (obviously) need to be be pretty bulky for the fluid capacity.
>>I think a large Kelly would be an ideal piece in a home kit for both water boiling to purify after a storm and that all essential cup of tea, cocoa or coffee while the lights are out.<<
I hadn't intended to use it for purifying, though the large version, used outdoors with lots of fuel available, would probably be very efficient for this. We're pretty well set there- three different sizes of Katadyn filters, and about 275 gallons of water in storage, not counting the water heater contents. :-)
All of this was just spawned by getting up in the morning during the blackout, and being reluctant to do anything as energetic as unpacking and filling the (Alpaca) kerosene stove, waiting for the wick to saturate, and firing it up, all before coffee and tea. Not having anything else at hand, I made a quick hobo stove by church-keying holes in a smallish coffee can and burning Sterno in the bottom. This brought to mind other occasions when the power had been out in the morning, but we suspected it was coming back on soon, and it wasn't worth breaking the serious gear out.
While I anticipate mostly stashing the kettle against this sort of thing, where I'd be using it indoors, with Esbit tablets, on a range, the versatility for camping etc. appeals to me.