Red devils and midas, in the pure forms, are reasonably distinct from one another. however, throughout their duration in the aquarium hobby, they have become so heavily hybridized between one another that it can safely be said that any RD/midas that didn't come from a few select fish-suppliers is a hybrid.
Midas are more omnivorous in nature, they have a relatively short U-shaped mouth and chunkier, square-shaped body. Red devils are much more suited for predatory lifestyles; they have an elongated snout that looks more like a V (than a U..) when viewed from above, and their body is more slender and streamlined, and they have HUGE lips. Red devils also grow a couple inches smaller than midas.
But the fish you have are almost certainly hybrids. Nothing wrong with hybrids, thats what most ppl have anyway.