I've never tried the yowie style, but I was given a second-hand pair that look a little bit like the second from the left of these:
(I don't weigh much, so don't need the really huge ones).
I've only used them twice, but they've been fantastic. The bit that your boots strap into is hinged to the main flat part, so that while the flat surface spreads your weight over a large area of snow, you can still move your foot in a very natural way, and walk perfectly normally. Ie, not matter what the angle of your foot, the flat surface is always flat against the snow when your foot is down.
They weigh very little, and I would always take them with me if I thought there was a good chance of deep(ish) snow. When walking in a group with others who didn't have any snow shoes, I spent most of the time waiting around for them to catch up wading through the snow, while I walked across the top of it. This was around the northern end of the overland track, particularly just around the west side of Cradle, where the snow is often quite deep.