I had offered to pass on some info from a friend who owns an R, lives in Burlington VT, and is a real serious car guy. The other cars in the garage that get driven in the winter are a BMW MX5, and a Ford F250. in the summer, add in two Porsches, and his wife's AMG 63 wagon.
He runs the 19" summer rims, and a summer high performance tire from May though September. In October he swaps on Nokian WRG3's, in a 225/45/17, mounted on what he said was "a cheap 17" aftermarket rim." The reason that he runs the WRG3 is that he does a lot of driving on dry roads in the winter. More so than driving in deep snow, or snow storms. If the snow is deep, and stormy, he and his wife will drive the truck and the X5. If he were going to drive the R in any kind of bad winter weather, with no other options, he would go with a 17" Hakka R3. Either way, he would never run the 19" rim and short sidewalls.
He has had great experience with the wear on the WRG3's. That's been our experience as well. He does not worry about driving 300 miles in 60-70 degree weather, and driving on ice and snow the next day. BUT, the tire is NOT as good in deep snow as a dedicated top quality snow tire. Is it good? Yes, really good. We were chatting and agree that when new, they are really good. And they tend to be real good for a few seasons, and maybe 40K or so miles. Then, they lose something in snow. On ice, in slush and packed down snow, they are abut as good as the Hakka R3, in his opinion. Hie comment to me was that in year one, the WRG3 might 90% of the performance of the R3. Maybe 80% in year two or three.
And nowhere near as good as studded Hakkas, which he's had experience with on his former S4 Avant.
If I owned a R, I would NOT be wiling to give up the top end summer performance. I would have bought the car primarily for the summer driving {or late spring and fall.} And I would want to maximize my winter performance, reliability and safety. My issue has always been that where we live, and drive to ski, I can often see a 60 to 80 degree swing in temperature in a couple of days, at certain times of the year. I have almost felt many snow/winter tires melt away. And I've been caught in a fresh 18" of snow in April many times. If I lived in the mountains, I'd run studded winter tires, right through mud season. I'd mount them as soon a snow was likely. But I don't. I live next to the ocean, near Boston, and 225 miles north, our ski home is a completely different climate.
I think this choice depends on what your winter driving will look like, best guess. Having a son who lives in Truckee, no chance would I run summer tires there or an "all season" tire with a summer bias. He runs studded Hakka's on a Tacoma. Tank. Last summer he bought some WRG3's for his GF's Outback 3.0R. They were great , other than in the deepest snow, or steepest grades {like their driveway!}. And they were great for driving when it was dry, or warmer. Now, he also lives up on Donner Lake.
Probably confusing, but I would absolutely run two sets of wheels and tires on the car. Then again, I don't know what the motivation was on buying the R, which can impact your thinking. I have an 80 year old neighbor who rives an Audi RS4 cabrio, "because she loves the color." Not why a lot of people buy them, but it works for her.
I realize that a good set of tires and some rims might cost $1000-$1200. So maybe $250 or so a season? I think it's well worth it. Just my $.02.