Originally Posted by 986Jim

Actually a taller wheel does have a larger contact patch. It doesn't really make a whole lot of difference with winter tires but I will explain how it does anyway.

A taller tire for more contact is generally only used in drag racing circumstances. If you are running a full slick on your car and want more traction a taller tire will provide that better than a wider tire. Lets say you were running 24.5 x 8 x 15" mickey thompsons on your drag S4 lol. For more contact you would be better off with the same tire in a 26" setup (so 26 x 8 x 15) than you would be with a 24.5 x 9 x 15" slick. A taller tire provides a longer foot print to the ground which is more advantageous than a wider footprint is in terms of traction.

With that said, on a winter tire where the tire shedding snow is the issue, a thinner tire is the best option. The best tire is the thinnest knobbiest tire you can fit on the car. So if you can get a 205 on it vs a 225 then that would be the way to go, just make sure to maintain the overall height of the OEM wheel or you can throw the electronics (speedo etc) out for a huge loop.