Hmmm...I have Metal Rock (I have never seen the other one), and it does go on pretty dark. When I first tried it, it looked like my face was dirty, but I just blended it more and used less, and it worked out. I think if you use a light hand, it is so very pretty as a bronzer. It also makes a good eyeshadow!
i'm an nc42 and metal rock is too dark unless i have one of the lighter MSFs over it (i.e. new vegas or shimpagne). so ceylon is freaking perfect. gorgeous glow, but still looks very natural. stereo rose and gold deposit are other favorites of mine.
metal rock needs to be using very sparingly. a little goes a long way. im an nc40 and adore my so ceylon but find i have to put quite a bit on to actually show wheras metal rock doesnt at all