Gold nori, which is really kinda actually black nori if you look at it, is more expensive. When I first started making my own sushi, I assumed that the higher price meant it was better. It ain't necessarily so!
The green nori is thinner (which probably accounts for the lower price?) and tears a little more easily, but it is SO TASTY. If you spread rice onto the nori when it's still warm from the rice cooker, it releases the most delicious smell. Assuming of course you LIKE the smell of nori. I suppose someone new to sushi might prefer the less scary gold nori, which doesn't look or smell like seaweed. ;)
As far as I can tell from my limited sources, gold nori is roasted for longer, which is why it's darker. I suppose that's why more of the seaweed smell is erased, too.
Disclaimer: I am (obviously) not an expert. To the best of my knowledge, everything in this blog is true. If you know better, please do leave a comment and correct me!
