Benefit of Lower Unsprung Weight?

[Johnno3]

Hi,
I’ve been using 15” mags with semi slicks in club motorsport, and was wondering about the benefits of lowering the unsprung weight by switching to 14” mags. (The consensus seems to be that lowering the unsprung weight is beneficial.)
Some details:
195/50 x 15 tyres. Combined wheel and tyre weight 16.75 kg (37 lbs).
185/60 x 14 tyres. Combined wheel and tyre weight 14.5 kg (32 lbs).
That’s a weight saving of 2.25 kg per corner, BUT with the 14s the sidewall is taller and the tread width slightly narrower. Any thoughts on how they might compare assuming an identical make of semi slick?
I’ve run both 14s and 15s in the past with semi slicks but no back to back comparison available.
(The car is a sedan weighing about 900kg, runs about 1.5 degrees negative camber, stiffer than standard suspension and has OK power.)

Thanks,