New snow tire question - size

[ricematthews]

Since we've been on the topic of snow tires, I have a question about sizes.
Has anybody out there used a 215/55/16 snow tire on an A4Q?  I think this is
the stock tire size for an A6 and for the new A4.  I can get a decent deal
on
a set of Dunlop Winter Sports in this size and I wonder if it's worth it or
if I should really stick with the 205/55/16's (diameter difference seems
manageable - I'm more concerned about snow traction with the extra width).
Thanks!
-Mark