By the way, given unsprung weight is so vital to handling, does anyone know the weight of Watanabe wheels in 15 and 16"
I spoke to Ben Zed and he said the Rota Grid is 9kg, and Rota RB is only 7.5kg ... both these are getting pretty light.
Despite aesthetics, weight will form a big part of my decision.
For a road car the difference won't be too much between good quality rims that are only a few kg apart. If you are really serious about unsprung weight then you will also be looking at saving weight with changing your standard brakes for light weight calipers and hubs with nice two piece rotors and hats to reduce the weight.
Reducing unsprung weight really only becomes and issue with race cars where a small weight cahange can really upset the balance of a highly tuned suspension system, think open wheelers and some sports cars (Le Mans prototypes).
I run Simmons wheels as my dry set up which weigh around 8-9kg. I couls have go the light weight rims fitted to the centre which would have saved me about 2kg a wheel, but the trade off is strength. I wasn't chasing the time that the weight saving would provide for having to replace rims a lot more often from hitting ripple strips and so on on the track.