Silver. The space gray doesn't seem very gray to me, and I like the white screen that blends into the generally light colored iOS 8. I considered gold for a bit and once I saw it in person saw how light it was but the lines on the back still didn't look any better.
I will only get colors that allow a black front. Because the arguably too big bezels fade away from view.
The white bezel stares at me in the face mocking me withs it's too-bigness.
I had wanted silver to match my Mac and iPad and just because I like the color but all best buy had were gold ones so I just took it. at least it's still white on the front,never had a gold phone so it's taking some getting used to