|Sugarpill on the left, MAC on the right|
I swatched these dry and without primer. Photo is taken with natural light near a window. You can see they look nearly identical. Soot & Stars is actually quite a bit more pigmented and a little darker than Dark Soul. I had to build up the pigment quite a bit to make it as opaque as the shadow.
MAC Dark Soul pigment is available for $21/0.26 oz.
Sugarpill Soot & Stars pressed eyeshadow is $12/0.12 oz. or for $34 as part of the Cold Chemistry palette with three other beautiful shadows.
I received the pigment as a gift, and we all know I purchased the Cold Chemistry palette as soon as they released it on their site. But if I had to choose between the two, considering quality & value, I would definitely re-purchase the Sugarpill palette.