Do Sparklings have better stats in Aniimo?

The shimmer changes how an Aniimo looks and nothing about how it fights. A Sparkling and a standard copy of the same creature bring the same stats into combat, so for team building you can treat them as one creature in two colours.

The same applies to the rarer styles. Dazzling and Shadow roll less often than Sparkling Types 1 to 10, but they are still only appearance. Sparkling Pigment rerolls the colour of an Aniimo that is already Sparkling. It does nothing to its stats.

Turning an Aniimo Sparkling does not cost it anything either. Applying a Prismana Orb to an existing Sparkling Aniimo gives you a Sparkling Prismana and keeps traits like Alpha status and perfect potential.

Why the Sparkling Cube muddies this

The Sparkling Cube is a separate case. It has a guaranteed 100% catch rate, and it may also guarantee perfect potential and perfect stats. That part is not settled: it is described as always guaranteed since the launch update, and also as still able to roll imperfect stats, Alphas included. It never lowers quality. If a creature caught with a Cube ends up with better stats, that comes from the Cube's roll and not from the sparkle.

Cubes are scarce, can be bought with real money, and are harder to get than standard Anipods. Save them for Aniimo you will actually put on your active team, like confirmed meta picks or Alphas with strong core skills. Don't spend them on every Prismana, first-time Alphas or early monsters nobody has tested yet.

Not settled: Sparkling status itself adds no stats. What is not settled is whether a Sparkling Cube also guarantees perfect potential and perfect stats on whatever it catches, so a Cube catch may come out stronger than a normal catch for reasons that have nothing to do with being Sparkling.