Hey there. Finally I have enough time to write this down and show you some pictures. :) First comparison I did with Galaxy girl and Formidable, because I just wore Space Cadet and wanted some change. So here it is ...
This is taken outside, I marked the fingers, the order is the same on every photo.
On direct sunlight (again L to R: MAC, Orly, MAC, Orly)
Play of colours in the finish. (MAC, Orly, MAC, Orly)
The blue shimmer. (MAC, Orly, MAC, Orly)
I have no idea why the pictures aren't clickable. I left them large so you can better see the comparison, but now the blogger won't let it change into original size in a new window. I'm really sorry about that, I'll try to fix it. o.o EDIT: did fix it. Man, it got personal!! They are klickable now. And huge. o.o
I did three coats of both polishes. I'm wearing it whole day long now and I think it's safe to say they are 100% dupes. The shimmer is the same, the finish, the base colour. Even first and second coat are the same - same amount of shimmer, same precentage of cover. Frankly, if I haven't wrote down on which finger is which polish, I'd have forgotten the order by now (luckily I did write it down, since I knew I won't be able to publish pictures right away).
I love MAC's brush! It was much easier to apply the polish. Otherwise all the same as Orly. I cannot judge the drying time, because I used top coat as I always do if I put more than two coats of polish. And the colour, well, I really really don't like it. I wasn't too crazy about Galaxy Girl's bottle (same goes for Formidable!), and I'm even less crazy about the colour on the nail. I'm thinking it's gonna go fast. I really don't like it on my nails.
All in all it's basically a decision about a brand, since the colour is the same. Which one, if any one, will you be buying? To you prefer MAC or Orly and why, if may I be so curious. ;) :)
Thanks for reading, have a good week!