I would say not terribly similar. I own both and don't really consider them to be "dupes" of each other. Coralista has a more creamy texture to it. The shimmer is much more fine and and the blush itself is more pigmented. As for the orgasm. It is sheerer in color. It has bigger pieces of shimmer. Still beautiful but much different. I would say coralista has more of a true coral/peachy tone and orgasm looks more pink compared to coralista. They are both beautiful.
I would agree that Coralista has much less shimmer (it almost looks matte when applied) than Orgasm, and Orgasm is more of a peach/pink, while Coralista is more coral. Personally, I like Coralista much better, as I feel that a lot shimmer on the cheeks doesn't look natural, and I love the coral color for summertime. Hope that helps!
I wouldn't call them duplicates at all. Nars orgasm is more similar to tarina tarantino parasol and thebalm hot mama then to coralista. Orgasm is a shimmery peachy-pink color whereas coralista is straight up coral with a glow and no shimmer or glitter.
pic is from goggle images