The odds of making a visual morph in the first generation with a co-dom/dom or whatever mix of the two are much higher (as opposed to producing a normal, or one that looks like only one of the parents).
With recessives it's a bit longer, because unless both parents carry at least one of the recessive genes then you will get hets and normals that will look the same otherwise and you'll have to go for another generation to prove them.