Hi Dave. Actually the three shell jackets would have been equivalent in terms of their basic windproofing function in these conditions. Waterproofness wasn't required due to the low temps. Some ability to shed snow is however useful to avoid excess moistness due to melting, when entering a warm space. The differences were more to due with the style of jacket and the type of activity.
The snow smock would have been adequate as my only shell, however its quite bulky and despite my modifications not quite as convenient to wear as my civvy shell. If I had to choose just one, I'd probably take the snow smock.
The 'civvy' jacket is a Patagonia Dimension MARS soft shell, which is shower-proof and a great all-round garment I use virtually every day. It has a large well-designed hood and very large front pockets, and I found it excellent for these conditions. I wouldn't want to wear it however, for extended physical work in the woods or around fires too much, for fear of damage, as its synthetic.
I also took my normal temperate conditions cotton shell smock, as it's a closer neater fit than the snow smock, thinking this might come in for physical work in the forest, however I didn't use it. I think if conditions had been very mild (>-10), I might have used this as a windproof with just two wool layers underneath.
The gaitors did get a bit damp/frozen at the bottoms, snow tended to stick to them and form icy scabs. They needed more cleaning off with my snow brush than the other garments.