I find that the heat retention variables are not that important because the shave is over before there's significant cool down. What I like about the Georgetown scuttle is the stopper and the finish (it's from a mould not hand turned) . You may not think the stopper is all that important until you go to make lather and you have water splashing around everywhere. Plus, this way you can pour hot water into both areas and pour out the water your brush was sitting in without loosing the hot water in the inner bowl...very handy.
Nothing in life is so exhilarating as to be shot at without result. --Winston Churchill