I just did a Live Chat about this same questain! The girl said it was different from Blot in that it doesn't have any oil-control properties and it gave (in her opinion) a bit more coverage although it was still very sheer. She said it's more of a finishing powder than a regular pressed powder. Because of that I deceided to pass cause I need oil control since it gets hot where I work.
I was in the store just like an hour ago playing with these and honestly I played with these and brought my old medium msf and seriosuly on the skin they looked excatly the same.. couldnt tell which side was which so if you have the msf.. these are a big pass.. the only thing I bought was rare and refined from this whole collection.
I got my Light mystery powder today and I really like it - it gives a nice matte finish and I think that I would be able to easily wear it alone on days when I don't feel like doing full foundation. To me the price is worth it since it comes with a refill and can be refilled later with different compact powders.