Yea, winter traction is all about PSI between the tire and the ground. Reducing the tire's width, reduces the square inches of the contact patch, therefore increasing the PSI.
You also want the tires to flex, so the more sidewall the better.
The exact opposite of summer traction.
If you were to spec a winter tire/wheel set (through Tire Rack or similar), they would recommend the smallest wheel that will fit over the brakes. So if you get enough snow to justify a winter setup, that's something to consider.