Just a data point. I wrote this down a few months ago and am posting it now.
16" OEM wheels with Dunlop M2 winter tires:
38 lbs front
41 lbs rear
17" 2001 OEM standard wheels with Kuhmo Ecsta 712 tires:
40 lbs front
48 lbs rear
So, all told, the difference in unsprung weight is 18 lbs.