While applying Mentality Tempest (shown on tuesday), it reminded me somewhat of OPI Every Month Is Octoberfest, so I decided to compare these two.
I used Every Mont Is Octoberfest on my pinkie and middle finger, Tempest on my ring and index finger, two coats each. Since the OPI is shiny and the Mentality matte, I added H&M Matte topcoat on my pinkie and KBShimmer Clearly On Top on my index to be able to compare the two polishes both in a matte and a shiny version.
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| left: OPI right: Mentality |
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| left: OPI right: Mentality |
As you can see, the OPI is a little darker than the Mentality, plus it has a purple base, whereas the base of Tempest is blackended/dark grey, so the OPI looks more blue/purple toned than the Mentality. The shimmer particles of Tempest are bigger, so this polish reflects the light better than the OPI.
Conclusion: these two polishes are similar, but not quite the same, so no dupes. Do you need both? Not really, you can substitute the other with a matte/shiny topcoat. Is it justifiable to want/have both? Absolutely, they're still different enough :-)