Miracle Cube vs Super Miracle Cube, What do you expect?

The cubes description tell you that they have an increased chance to make the item move up in tiers, hence the whole argument. If it turns out you can only use the cubes on unique items this whole thing would be moot, but we are not there yet.

I remember a KMSer(I think it was Casper) who posted that he used significantly less cubes to get rare->unique with super miracle cubes.
It remains to be seen whether this difference offsets the added price.