So, here's my conclusions... and I could be wrong; I don't have recipes, but here we go!
Party Like It's 1999:
This polish is a little lighter, so while it leans more on the creamy side of crelly, elements stand out against the base color a little better.
There seems to be less flakes in this polish, so if you love the "less is more" look, this is the choice for you!
There might be a neon pigment incorporated to this base color; it does have a brighter quality to it, even in lower light.
Beyond Imagination
While it still has a "crelly" formula, this one leans more in the direction of jelly. Therefore, you can see through each layer a little better.
There is an abundance of flakes in here. Sometimes they can be hard to spread out evenly across the nail, but if you're hoping for coverage from added elements as opposed to base color, this is the choice for you!
There is a slight purple tone to this polish. This may be solely based on my skin tone, but once it's built up I'm getting more purple than pink.