I agree with blindkarma.
My 2011 RD came with 255/45R20 tires which I use for the ice/snow free months and I switch over to 235/60R18's for my winter tires. Overall diameter is the same so the speedometer/odometer are accurate.
As you noted, there are very few options for 20" dedicated winter tires and several options for the 18". Doesn't take much time to switch them over twice per year. These cars perform amazingly well on snow and ice with a good studded tire.
My 2011 RD came with 255/45R20 tires which I use for the ice/snow free months and I switch over to 235/60R18's for my winter tires. Overall diameter is the same so the speedometer/odometer are accurate.
As you noted, there are very few options for 20" dedicated winter tires and several options for the 18". Doesn't take much time to switch them over twice per year. These cars perform amazingly well on snow and ice with a good studded tire.