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

Did you not read this topic? "Master Cubes" have a greater chance to increase item rarity / rank than compared to normal miracle cubes.
It's recommended to normal cube to Epic and then "Master Cube" all the way to Legendary.

I thought the rate for Master Cubes from Rare -> Epic was something high like 25%?
In that case, wouldn't it be better to cube with Master Cubes as you should expect to use about 4 of them?

From experience, it takes me ~20-30 cubes to get an item from Rare to Epic.