Tires have evolved a huge amount over the years. Today's tires are far more capable than they were even 10-years ago. That being said, your neighbors in Ontario, Canada REQUIRE snow tires. IMHO, they probably realize the benefit. They are insurance, but even winter tires (the industry hasn't called them snow tires for years!) because they are optimized for colder temperatures AND inclement weather. IOW, you'll be able to stop faster on dry roads when it is cold and have more traction when the roads are nasty. With the high torque at low rpms on the i3, if you stay in comfort mode, they will definitely help. If you switch to an eco mode, where the throttle is dampened somewhat, it's easier to get started when the roads are slick. They are insurance...you may never need them for your car, your health, or your home, but are nice to have. Snowy roads at 32 are more slick than those colder because the weight of the car tends to turn a thin layer to water...water on ice is nasty stuff.
You may never need them, you may wish you had them. Only time will tell. The all-seasons aren't horrible in the scale of things, they're just not as good as the winter tires.
With the cost of remounting seasonally, especially with the TPMS where the industry recommendation is to change out the stem (about $12 each) each time, throw in the opportunity to nick up a wheel or do a lousy job of balancing, a complete set doesn't start to look bad, and, you might get a better return as a private sale at the end, verses a trade-in.