Wide tires make less difference now, partly because even the lowliest econohatch may have low profile tires. In deep snow or heavy slush narrower tires offer an advantage. The rest of the time I find stock sized winter tires work fine.

The XF is transformed on winter tires even compared to the stock all season tires fitted to the luxury and premium level cars. There will just be no meaningful comparison between any winter tire and the high performance summer tires fitted to the XFR. I had a set of Pirelli P7000 fitted to my turbo SAAB one of the top winter performers I have ever driven and it wouldn't even move on snow. Period. No movement at all. Now a SAAB 9000 is nearly as good as an awd Audi for traction in winter, I know I have one of each.

It isn't the car, it's the tires.

No rwd car in the world is going to perform in winter as well as a fwd or awd car. Regardless of tires fitted.

I will say that most SUV have seriously inferior winter handling to my SAAB, let alone my Audi. They don't corner well and they don't stop well. In winter, the jag will out corner and out brake any SUV on the market other than a Cayenne, Audi or Range Rover if fitted with winter tires, unless you are trying to drive fast in the deep stuff.

And just BTW, that straight on steering effect in deep snow affects any vehicle with no drive to the front wheels. That's just physics and winter tires make no difference to that problem. It is caused by lift effects on the tire in the deep stuff. Fwd or awd can chew their way around but rwd just cannot.

 

I hate to admit it, But I am looking at trading my 11 XFSC for a 11 Audi S5 Convertible (Prestige). I know its trading down but also up in a few ways as well. Waiting to get blue book on the car now as it doesn't seem to have one. I wil miss the pure performance but then again I can let my son drive the new one and daughter will love the ragtop.. I must admit i wont miss the cheesy nav though..

 

In response to OP's original question, I ended up with 255's (winter tires) all around on the 20 inch Selena wheels. Haven't had enough snow or ice to test them.

 

I took a long look at buying an S5 coupe. Beautifully styled car. The interior is not as nice. One of my partners had the convertible. I wouldn't trade at this point given the choice. What is it about the S5 that is tempting you to trade? (thread hijack).