MAC Cham-Pale Soirée Nail Lacquer vs. Orly Rage - Comparison & Possible Dupe?

Are we related? MAC Soirée and Orly Rage.

I recently picked up the two nail lacquers from MAC's Cham-Pale collection (see my review here).  One from the collection, Very Important Platinum, was an epic application fail.  Streaky, thin, blech.  Reminded me of how bad MAC used to be at nails.  Then was Soirée a pretty dusty-rose metallic foil.  Very pretty on, but it seemed somewhat familiar.

Digging through my stash, I found Orly Rage.  A gorgeous rosy silver foil from a few collections ago and still easily available.

I decided to do a side by side comparison since one is about half the price of the other.  From the bottle, they seem almost identical.  You can see that Orly's Rage is more silvery and the duochrome particles seem finer.  Soirée seems more rosy and dustier, but overall they are very, very, very close.  Maybe fraternal, not identical, twins.

Left to right: Soirée, Rage, Soirée, Rage.

I think the ring finger shows off Soirée's dusty, copperiness best.  However, from a distance (of 6 inches), they look almost the same.  I think most people wouldn't even notice a difference.  Click on the photo to enlarge.

 A photo of all Soirée.  
You can see the copper and dustier elements in the shade here.

All Soirée.  Let's party! 

MAC Soirée is $13 for 10ml 0.34oz, limited edition at MAC counters and MAC online.
Orly Rage is about $7 (depending on store) for 0.6oz and available at salons and Sally Beauty supply.

If you missed the review of Soirée and Very Important Platinum, click here.

How close does a dupe, comparable have to be to cancel out the original?  Do you go by price difference, meaning the cheaper one?  Or sometimes do you just have to have it?