Disco Lane is only available as a part of the The After Party set. I found mine on Sephora.com. Orion's Belt is available singly, mine came from OverallBeauty.com. They are similar, but far from dupes.
It won't show on the swatches nearly as well, but Disco Lane isn't as black. It's more charcoal. It's very dark, it's almost black. Orion's Belt is simply a darker black. I know you know what I mean just as much as I know how ridiculous that sounds to someone without Nailosaurus Opticus.
Orion's Belt is on my middle finger, Disco Lane on my index. The holo is a lot more dense in Disco Lane, it has more fire. There is a downside to this, though. I'll explain in a minute.
This is one coat so you can see the opacity of the bases to these.
Orion's Belt is simply less aggressive.
This is with a coat of Seche on each. As you can see, it tones down the roughness on Disco but Orion is losing some of it's sparkle to the top coat. Hm. They both actually lost quite a bit of their glamour under the Seche. Maybe a different top coat?
So there you have it? Will you pick these up? One or the other? I'd love to know!