I have the gold...coming from a black/slate iPhone 5 (then previously a white 4S and a black 4). I tend to alternate, with the S models in white, the number upgrades in black.
With the 4/4S in white vs black, I think the black looked clearly better...the all white design was a little bland for me on my 4S.
With gold vs. space gray (and silver), I think it's a very different ballgame (as was the same with the slate vs silver last year). Both gold and space gray look really, really good. In the store, when I looked at the whole rows of iPhones, i thought the space gray looked fantastic, with the silver actually looking best with the gold last. After having the gold for a week, and not having things all lined up in a row under fluorescent light, I think the gold looks utterly fantastic, and now when I see a space gray 5S, while it still looks good, it also looks kind of boring. The gold 5S has a very subtle sophistication, and the way it changes the look depending on the lighting is really quite beautiful.
I think if you've had black phones forever, you sort of owe it to yourself to pick up a gold or silver 5S...if you've stayed with white for a while, you owe it to yourself to get the space gray.
While I somewhat regretted getting the 4S in white just because it wasn't all that exciting, I really, really like the gold, and am glad I eventually went that way, because in the beginning I was all about the space gray.
