At 490 grams, the DH- 3N80 gives the 570g SON 28 a good run for the money and quality is very good. I'm not aware of any resistance comparisons for this newer version. We know that the SON was slightly better than the DH-3N30, in these tests (PDF)

However, the new SON 20R, weighing just 385 g, can be confidently used with the new LED lights as they come up to power at lower speeds than halogen. How much the lower wind resistance comes in to play is of less interest than the lower drag from the generator itself, due to using a hub designed originally for smaller wheels.

And who could resist the bling factor of this combo?
I might have to build a new bike just to match!