I was driving multiple Subaru AWD for the last 17 years exclusively.
GTA/Mississauga area.
BRZ/FRS can not compare to them in snow. My first snow last winter in RWD was an eyes opener how good AWD in snow compare to RWD.
And I use winter tires on all 4 wheels.
Multiple issue to look for especially if you switch from AWD:
1) Small incline with snow/ice and no go from stop in first gear. BRZ/FRS acceleration pedal is not linear. It gives accelerated input in the beginning. I wished we had snow mode with reduce acceleration input in the first 20%.
With boosted engine this will become only worse.
To overcome it:
a) Start in second gear (bit more wear on clutch)
b) Turn off traction control (left button, just for start)
2) Going through fresh snow stability. It happened only 2-3 times last year. About 10 cm of fresh snow. Max speed I was able to go straight is 30-40km/h. After that ass starting to go left and right and Traction control getting in a way and cutting power off. On AWD Subaru you would not even notice it.
What to do:
a) if you are brave turn traction off and use your steering to catch your ass. After 20 min of driving I had sweaty back and stiff neck. Maybe it is fun on empty streets, but not when you have cars, buses and curbs all around you.
b) accept your car speed limit.
3) How do you use handbrake to correct under-steer? In AWD/FWD I could engage handbrake and give a bit of gas to finish my turn and stop front from under-steer. Yes it overload AWD central diff but was working.
a) Maybe clutch-in when I pull handbrake just to nudge it? but it is not the same feeling.
4) Be careful on overpass bridges. They ice and I was loosing traction going in straight line. Those icy connection overpass from 403 to 401 are scary on a fresh morning ice with other cars spinning out of control around you.
Now good things:
1) It stops way better. Lighter and maybe also because you tend to go slower. On AWD Subaru I got caught few times when I become to confident and was faster then I supposed to be to stop where I should. Road before traffic light tend to be more icy due to other car sliding and polishing it.
2) Does not under-steer in snow that easily. You actually can take corner with faster initial speed. It's turn-in is better. So I don't actually need to help it with hand brake. But forget about accelerating out of it. Had to wait to be completely straight before putting any pressure on a pedal.
3) if you get in a trouble it is easy to apply correction and put it back in line.
In short.
I would not go up to snowy/icy hills in it if I can help it. I will drive slow like everyone around me and probably a bit slower
But if I got too annoyed I always can switch to my wife's Legacy (generally boring car, but still fun in snow). If I need to go to Blue Mountain skiing I will double check the weather and maybe call my buddy with AWD.
With GTA roads driving BRZ/FRS is totally fine 90% of the winter. The rest 10% just has to be slow and sometime maybe take a bus. It's one of few compromises of owning this car.
Gone those days when I was praying for snow to fall and get into my Subaru...