I bought the gold 2" after reading the gold plates would move more smoothly through the hair than the black plates on the original. I never personally compared the two, so I don't know if the gold plates make that much of a difference, but since it was the updated model, I went with that.
If you go to the GHD site, there's a product locator and list of approved online retailers. I bought from GHD directly, not realizing they were located in Canada, and wouldn't recommend it because I ended up paying a currency conversion fee. Not substantial, but why pay it if you can get the item locally?