In case anyone is on the fence about this.  It's hard to tell from pictures what they really look like in person, but after seeing both I would strongly suggest that Crimson/Black is a better look.

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aww but I already bought the Cobalt/Black.

Heh... same here.  I actually bought the Crimson/Black for a friend and the Cobalt/Black for myself... but now I wish I could trade.  :)

Haha, I got a crimson/black :) (what the heck is this thread about, Nintendo DS? If that's the case I actually speak the truth, if the red is considered crimson O_O!)

My DS has a big ole ugly nerf protector around it. It helps me hold it with my large man-hands, as well as protecting it from breaks and falls while reinforcing the hinge.

The nerf protector is baby blue.

That's the best color nerf protector.

My DS itself is black, like my heart. Because I can say "black like my heart," black is the best color.

Crimson's better. But I still wish I got black cause I hate the roughness on the bottom of the crimson. I tried my friends black and it felt so nice and smooth.

I got the crimson/black one but in all honesty I prefer the original white one. Plus it matches with the Wii! ^_^

I also have a white one... let's trade.  :)

Cobalt/black is totally the way to go. My brother-in-law has the crimson and I have the cobalt. There's really no question. :P