The difference, by the numbers
Both have orange juice, lemon juice and grenadine. Only the Cinderella has pineapple juice and soda water; only the Pussyfoot has mint, lime juice and egg yolk. In parts, a Cinderella is 2¾ orange, 2 pineapple, 1 lemon and 2¾ soda; a Pussyfoot is 8 orange, 1 lemon, 1 lime and 1 grenadine. By volume, the Cinderella is 86% mixer and juice and 12% citrus; the Pussyfoot is 73% mixer and juice, 18% citrus and 9% syrup and sugar. That makes them close cousins on the ratio map.
They are about equally strong in the glass (both 0.0% ABV), and they hold about the same alcohol (0.00 standard drinks each). The Pussyfoot has more calories (about 172 against 76) and more sugar (20.3 g against 13.6 g). Both are shaken and served in a highball.