It's safe to say I'm a bit of a blush addict, so I try not to get dupes, we don't want anything going unloved now :) My Illamasqua Sin was a present from a friend of mine that I received a good while ago, after I took a good look, I saw a big resemblance to my Topshop cream to powder blush in crushed berry. After some comparing here's what I found.
Illamaqaua-left | Topshop right
Its clear to see that the topshop blush has far more of a pink to it, whilst the Illamasqua blush is more purple. This is a big contrast to how they look in the pan as they look near identical. Now you can see that once blended out, the differences become less apparent, however they are still noticeable.
However both are great to have in your collection.