I would say that at first blush (haha) my midnight musings weren't far off the mark. In the pan Peony Petal looks like a close dupe for Gaiety. However, the colors differ when swatched.
Gaiety is a lighter blue-based pink while Peony Petal is a darker blue-based pink that seems to have a little more red in it.
Outdoor Lighting Direct Sun
I would definitely say that these two beauties fall within the same family of pink hues, but there is no comparison between the quality of these two blushes, period. Gaiety is soft smooth and silky- it applies like a dream, and is without question one of the greatest blue-based pink blushes EVER! For an outstanding review of Gaiety see Zuzu*s at Everyday Beauty- if that doesn't make you run out and buy Gaiety- nothing will! While Peony Petal is a gorgeous color it is stiff and chalky to the touch- so you are deprived of the same outstanding tactile experience that is immediately noticeable with Gaiety. However, Peony Petal applies and wears beautifully- and though I expected it to be patchy and skip it did neither.
Overall assessment: Peony Petal is not an exact dupe for Gaiety, and while both are gorgeous- if you are forced to choose between them Gaiety should be your blush of choice.