(1) Total vehicles per day and total vehicles per hour during peak travel times
(2) Total miles of road in region under consideration
(3) Frequency of snow
(4) Volume of snow
(5) Mean number of days until snow is expected to melt if untreated
(6) Number and grade of hills, and location with respect to arterials/population/jobs
Basically, if you have a lot of miles of road, but not many vehicles, then you won't plow or treat to bare pavement; you'll just make your drivers drive cars that handle well in compact snow and ice, and expect them to run a different set of tires during snow season than during the rest of the year. Public buses might run chains part of the time.
If you have snow frequently, but at a low volume, you might not plow or treat, because it doesn't ever accumulate and it tends to blow off the roadway (but your roadways will probably be slightly elevated to exploit the wind factor).
If you have an enormous volume of snow, but only occasionally, you'll probably plow, because there's some risk that if you don't plow, then you'll get another enormous volume and roads will become impassably untreatable.
If the mean number of days until snow melt is believed to always be short, then you won't plow or treat, but you will be expected to forecast correctly and close everything for those days, because absolutely no one is running appropriate tires, has familiarity with running on compact snow and ice, the city won't own vehicles to plow and treat, the money isn't in the budget etc.
So when a midwesterner (huge number of miles, comparatively small number of vehicles, frequent snow and sometimes high volume snow if lake effect, with months delay before full melt) critiques a southern state for handling things poorly, the midwesterner dismisses the importance of correct forecast, and advises an insane investment in cars/tires/training for all the drivers. When a New Englander critiques a southern state for handling things poorly, they understand the value of a good forecast, but don't really understand what happens at the kinds of temperatures involved: that seems too warm and too small a volume of snow to be a problem, and New Englanders have a very small number of days dealing with sheet ice or ice particles suspended in water (and when they do encounter those conditions, they have accidents comparable to a Seattle driver or Atlanta driver. Physics is physics.).
People in Seattle know not to go up and down (certain) hills in slippery weather; they spend a lot of time passing around media depicting what happens when you/the bus driver makes this error. They'll focus on Atlanta school buses being sent out on routes with those hills and no alternative plan.
Portland, Oregon's extremely rigorous growth boundaries take on a whole different meaning if you think about them in this context. Portland has ice storms, all the freaking time. You can't necessarily just salt your way to vehicular happiness, because the environmental destruction would be disproportionate (trees grow very slowly in the PNW, vs. the East Coast). I have to wonder if a compact settlement pattern was chosen because it makes those ice storms a lot easier to keep working and going to school through (walk/public transit, fewer vehicle corridors so more traffic per mile thus the cars warm the roadway helping to keep it ice free). Obvs, the geography of the area has a bit influence as well.
After thinking about the southern storm while trying to resolve conflicting opinions from people whose adult life was spent in different regions, I have concluded that R.'s response is classically New Hampshire/central-western Massachusetts: a compromise between treatment and an expectation to have good tread on the tires and show good judgement about deciding when to travel, along with zero personal experience with school closures outside of Longmeadow (tiny, walkable) and Acton (less tiny, still fairly walkable, very flat). My response is Seattle (there's white stuff; just stay inside until it goes away) with a sprinkling of New Hampshire (if you don't keep the driveway down to bare pavement, you won't be able to stop before hitting something on the downward slope and that's part of the house up there) and a generous helping of Metrowest (hey, we pay money for you to keep these roads clear. Why didn't you plow again and when are you going to plow the rest of the sidewalks). My sister's response is southern: the government _will_ fuck this up, so show good judgment where your kids are involved and bring along stuff in case something happens along the way. Etc.
And then I'm a nerd, so I'm pro technocrats will solve this if we just get the right ones.