tents
It's all about where & how you plan on using it.
Back in the day, when I couldn't afford specialized tents, I used a $35 dome tent, with a 1/2 coverage fly for all 4 seasons. Advantage in winter is that you only need to cover the mesh with a fly - the rest can easily be a 1 wall design (because the precipitation is dry, i.e.: snow). I used that tent for 6 years.
So:
- if you plan on doing overnights above tree line, where wind is a factor: get a very sturdy & functional tent - it may be your only "safe zone" in bad weather, so you better be comfortable spending time in it.
- if you camp below tree line, but in heavy snow fall areas, you may be OK with 3 seasons, but ensure that you get the snow off the tent to keep it from collapsing. Note that 4 season tents have a load limit too, so don't think that a 4 season tent does not require clearing the snow off of it.
- if you are an occasional winter camper, in well protected zones, the only thing you have to worry about is the durability of the fabric in the temperatures it will be exposed to. Some people even use a tarp, or go without a tent completely.
the wall...........